A single-sex school teaches only boys or only girls. A coeducational, or coed, school teaches them together. The debate is about whether keeping the sexes apart helps young people learn and grow, or whether it holds them back and teaches them to see each other as different kinds of people.
Separate schooling has deep roots. Virginia Military Institute, a public college founded in 1839, admitted only men until 1996, when the US Supreme Court ruled 7 to 1 that shutting out women broke the Constitution's promise of equal protection.8 That same year, the Young Women's Leadership School opened in East Harlem with 56 seventh-graders, New York City's first new single-sex public school in more than 30 years.13
In the United States, public single-sex education grew after federal rules in 2006 allowed it, as long as enrollment is voluntary and families have a “substantially equal” coed option. At the time, one supporter counted 241 public schools with single-sex programs.3 In 2017, Education Week reported that federal data showed more than 1,000 single-gender public schools. Their students are mostly Black and Latino and are 1.5 times more likely than their peers to qualify for free or low-cost meals.4
Elsewhere the picture varies. In Ireland, about a third of secondary schools are all-boys or all-girls, yet no new single-sex school has opened there since 1998.2524 In New Zealand, about 98,000 of the country's 854,000 school students were in single-sex schools in 2025.27 In Saudi Arabia, classes are still separated by sex, although in 2019 the government let women teach young boys at 1,460 public schools.28
The research is fiercely argued. A 2014 review of 184 studies, covering more than 1.6 million students in 21 countries, found that the small advantages seen in weaker studies disappeared in the better-designed ones. “Our comprehensive analysis of the data shows that these advantages are trivial and, in many cases, nonexistent,” said co-author Janet Shibley Hyde.1 A 2005 review for the US Department of Education was more cautious: “As in previous reviews, the results are equivocal.”5
Supporters point to striking results. In England, girls were almost two and a half times more likely to take A-level physics if they came from a girls' school rather than a coed one.16 When Trinidad and Tobago turned 20 low-performing coed schools into single-sex schools in 2010, exam scores rose and boys were arrested less often.10 In New York City, the Eagle Academy schools for young men reported a 78% graduation rate in 2015, compared with 50% for Black and Latino boys across the city.14
Critics see a different danger. In 2011, eight scientists writing in the journal Science called single-sex schooling a “pseudoscience” and warned that separating children can increase gender stereotyping.2 The ACLU, a civil liberties group, has challenged single-sex programs in several states. “We all want to fix failing schools. But coeducation is not the problem, and single-sex education is not the answer,” said its lawyer Galen Sherwin.6
Key terms
Coeducation
Teaching boys and girls together in the same school and classes. The opposite of single-sex education.
Meta-analysis
A study that combines the results of many earlier studies to find the overall pattern, like the 2014 review of 184 studies of single-sex schooling.
Selection effect
When a school's results look good because of who it admits, such as richer or higher-achieving students, rather than because of what it does.
Peer effects
The influence classmates have on a student's learning and behavior. Supporters say the mix of boys and girls in a room is one such effect.
Gender salience
How noticeable gender is made in a setting. Research suggests that the more adults highlight it, the more children rely on gender stereotypes.
Gender-atypical subject
A subject usually chosen more by the other sex, such as physics for girls or modern languages for boys.
Equal Protection Clause
Part of the Fourteenth Amendment to the US Constitution, requiring states to treat people equally under the law. It was the basis of the 1996 ruling against Virginia Military Institute.
Pros and cons at a glance
Pro: make schools single-sex
Con: keep schools coed
Pro arguments
Con arguments
Key clashes
Most single-sex schooling debates are won or lost on these four questions.
1Do single-sex schools really raise achievement?
Both sides have studies. The fight is over which ones compare like with like.
Pro saysWhen Trinidad and Tobago converted whole schools, the same kinds of students did better, and girls' schools send far more girls on to physics.1016
Con saysOnce background and prior grades are taken into account, the advantage shrinks to almost nothing.119
2Stereotypes: does separation weaken them or strengthen them?
Both sides say they want to free students from gender roles.
Pro saysWithout the other sex watching, boys and girls are more likely to choose subjects that break the usual pattern.17
Con saysDividing children by sex tells them that sex is what matters most, and experiments show it makes stereotypes stronger.221
3Social life: protection or preparation?
A question about what school is for, beyond exam results.
Pro saysMixed schools expose students, especially girls, to harassment and pressure that get in the way of learning.2324
Con saysStudents need practice getting along with the other sex, and those from single-sex schools can find mixed settings harder later.22
4Choice or rule: should every school be single-sex?
Even people who like single-sex schools may not want them for everyone.
Pro saysIf single-sex schooling helps, it should not be a privilege for families who can pay private fees or win a place at a special school.
Con saysFamilies want different things, and US rules already insist single-sex classes must be voluntary, with an equal coed option.37
Around the world
The US: public single-sex schools and classes have been allowed since 2006 rules, if they are voluntary and a substantially equal coed option exists. More than 1,000 single-gender public schools were reported in 2017.34
Ireland: about a third of secondary schools and about 17% of primary schools are single-sex, but no new single-sex school has opened since 1998, and some, like CBS Synge Street in Dublin, are becoming coed.252426
England and New Zealand: both still have many single-sex state schools. In New Zealand they taught about 11% of school students in 2025.1927
Saudi Arabia: school classes remain separated by sex. Since 2019, women have been allowed to teach boys in kindergarten and the first three grades in an early childhood project.28
Debate tip: comparing countries is useful evidence on both sides. Pro can point to places where single-sex schools post strong results; Con can point out that most of the world, and the trend in countries like Ireland, is toward coeducation.
Discussion questions
For class or club discussion. There are no right answers; ask for reasons and evidence.
Should schools be single-sex? Explain your answer using at least one argument from each side.
If single-sex schools raised exam results by a small amount but made students more anxious around the other sex, would they be worth it?
How could you tell whether a successful single-sex school succeeds because of its students or because it is single-sex?
Should public money ever pay for schools that admit only one sex? Is that different from a girls' sports team?
How should single-sex schools include students who are transgender or nonbinary? Does this question change the debate?
Sources
American Psychological Association, press release on Erin Pahlke, Janet Shibley Hyde and Carlie M. Allison, meta-analysis of single-sex schooling, Psychological Bulletin, February 3, 2014. LinkPeer-reviewed research
Arizona State University, “Single-sex schooling does not improve academic performance and can lead to gender stereotyping, study finds,” on Halpern et al., “The Pseudoscience of Single-Sex Schooling,” Science, via ScienceDaily, September 23, 2011. LinkPeer-reviewed research
Education Week, “New U.S. Rules Boost Single-Sex Schooling,” October 2006. LinkNews report
Corey Mitchell, Alex Harwin and Francisco Vara-Orta, “Single-Gender Public Schools in 5 Charts,” Education Week, November 2, 2017. LinkNews analysis
Fred Mael and others, American Institutes for Research, Single-Sex Versus Coeducational Schooling: A Systematic Review, for the US Department of Education, September 2005. LinkGovernment report
ACLU, “ACLU Launches ‘Teach Kids, Not Stereotypes’ Campaign Against Single-Sex Classes Rooted in Stereotypes,” May 21, 2012. LinkAdvocacy group
ACLU, “Doe v. Vermilion Parish School Board,” case page. LinkCourt case, via advocacy group
National Constitution Center, “United States v. Virginia (1996),” Supreme Court Case Library. LinkCourt ruling
Supreme Court of the United States, United States v. Virginia, 518 U.S. 515 (1996), opinion of Justice Ginsburg, in Constitutional Law, University of Central Florida Pressbooks. LinkCourt ruling
C. Kirabo Jackson, “The Effect of Single-Sex Education on Academic Outcomes and Crime: Fresh Evidence from Low-Performing Schools in Trinidad and Tobago,” Institute for Policy Research, Northwestern University, Working Paper 16-23, 2016. LinkAcademic research
Chezare A. Warren, “Chicago's Urban Prep Academy, known for 100% college acceptance rates, put reputation ahead of results,” The Chicago Reporter (from The Conversation), May 23, 2019. LinkExpert commentary
ABC7 Chicago, report on the Chicago Board of Education vote to revoke the Urban Prep charters, October 26, 2022. LinkNews report
Pedro Noguera, “How a single-sex school in East Harlem offered young women a path out of poverty,” The Hechinger Report, September 5, 2016. LinkOpinion, board member
CBS New York, “‘Eagle Academy’ In The Bronx Among Schools Making A Difference In Lives Of Urban Students,” January 21, 2015. LinkNews report
UCLA Higher Education Research Institute, press release on research by Linda J. Sax comparing women graduates of single-sex and coeducational high schools, March 19, 2009. LinkUniversity research
Institute of Physics, It's Different for Girls, October 2012. LinkProfessional body report
Alice Sullivan, Heather Joshi and Diana Leonard, “Single-sex Schooling and Academic Attainment at School and through the Lifecourse,” Centre for Longitudinal Studies Working Paper 2008/3, Institute of Education, London, 2008. LinkAcademic research
Natasha Plaister, “How does performance in single sex and mixed schools compare subject-by-subject?” FFT Education Datalab, October 17, 2023. LinkResearch organisation
Natasha Plaister, “Do pupils in single sex schools get better grades?” FFT Education Datalab, May 12, 2024. LinkResearch organisation
Katherine Dix, “Single-sex schooling and achievement outcomes,” Australian Council for Educational Research, September 28, 2017. LinkResearch organisation
Penn State, “Highlighting gender promotes stereotyped views in preschoolers,” on Hilliard and Liben, Child Development, November 2010. LinkPeer-reviewed research
Anna McKie, “Students from single-sex schools ‘anxious’ in mixed universities,” Times Higher Education, December 17, 2018. LinkNews report
Ofsted, “Ofsted: culture change needed to tackle normalised sexual harassment in schools and colleges,” June 10, 2021. LinkGovernment report
Lunney, Gavin, Költő, Kelly and Nic Gabhainn, “Single-sex schools in Ireland: Exploring school & wellbeing indicators,” HBSC Ireland, University of Galway, May 27, 2025. LinkUniversity research
BreakingNews.ie, “Single-sex schools ‘outdated’ with calls to end them in next 10-15 years,” February 7, 2022. LinkNews report
Department of Education (Ireland), “Minister Foley welcomes the announcement that CBS Synge Street will transition to a co-educational Gaelcholáiste,” September 11, 2024. LinkGovernment statement
Ministry of Education (New Zealand), School Roll Returns, students by school gender at 1 July 2025, via Figure.NZ. LinkGovernment data
AsiaNews, “Saudi authorities to let women teach boys,” September 2, 2019. LinkNews report
International Coalition of Girls' Schools, “Three Decades of Coalition History: 1991-2024.” LinkAdvocacy group
Arguments marked “Evidence needed” are waiting for a source before this guide goes live.
