Single-sex or co-ed school? What the evidence says

The short answer

There is no reliable evidence that single-sex schools, as a type, produce better results than co-educational schools once you account for who they admit. There is reasonable evidence that the choice can influence softer things, such as which subjects children feel comfortable choosing, and plenty of evidence that individual schools differ far more from each other than the two categories do on average.

That makes this a question about your child and the specific schools on your list, not about which model wins a league table. Parents who put fit, culture, logistics and the quality of teaching first usually make a better decision than those who start from a view about girls' schools or boys' schools in general.

The Houseroom figures above show how the three groups compare across the independent schools we list. Read them as a description of the market, not as a verdict on single-sex education. The raw gaps mostly reflect selection: which families apply, how selective the school is, where it is, and what it charges.

Why raw comparisons mislead

Headline comparisons between single-sex and co-ed schools are dominated by selection effects. In the UK independent sector, many of the best-known single-sex schools are academically selective, long-established, located in or around London and relatively expensive. Families who can pay those fees and prepare for those entrance tests differ, on average, from families who cannot. A school that admits pupils who were already high attainers at 11 will post strong GCSE and A-level results almost whatever its gender model.

The same applies to our own numbers. If one group shows a higher median Houseroom Index score, that tells you the schools in that group include a relatively large share of strong, selective schools. It does not tell you that a given child would do better there than in a school of the other type with a similar intake. To answer that question, researchers need to compare pupils with similar prior attainment and family background, and that is where most of the apparent difference narrows or disappears.

Other things that drive raw gaps:

• Geography. London schools differ from those elsewhere in fees, competition for places and results, and our directory covers London much more fully than the rest of the UK. The London and outside-London rows above let you compare like with like.
• School size and age range. The co-ed group includes many nursery, pre-prep and prep schools, which usually charge less and are not selective in the same way; many single-sex schools are senior schools with a selective entry point at 11+ or 13+. That alone pulls the co-ed median fee down.
• Boarding. Boarding schools have a different fee structure and pupil mix from London day schools.
• Data coverage. Not every school publishes the same information, which is why the table shows how many schools each median is based on.

What the research says

Research on single-sex schooling is large, contested and often reported selectively. The honest summary is that careful studies tend to find small or no differences in overall attainment once pupil intake is controlled for, while some studies find differences in attitudes and subject choice.

International evidence. A widely cited meta-analysis by Pahlke, Hyde and Allison, published in Psychological Bulletin in 2014, pooled studies from many countries. In general terms, studies with weak controls tended to show advantages for single-sex schooling, while studies that controlled properly for selection found little or no advantage for either model in maths, science or verbal performance, or in attitudes.

OECD / PISA. The OECD's analysis of PISA data has repeatedly found that differences between schools in pupils' socio-economic background explain much of the variation in results between schools. When comparing single-sex and mixed schools, the practical lesson is the same: account for intake before drawing conclusions. You can explore the PISA material on the OECD PISA pages.

UK longitudinal evidence. Alice Sullivan, Heather Joshi and Diana Leonard at the UCL Institute of Education used the 1958 British birth cohort (the National Child Development Study) to follow people educated in single-sex and mixed schools into adulthood. They found single-sex schooling was positive for girls' overall qualifications at 16 but neutral for boys, and neutral for both sexes at later ages. It was, however, linked to gaining qualifications in subjects less typical for each sex, both at school and later in life. That cohort went to school decades ago, so treat it as evidence about mechanisms rather than about today's schools.

Subject choice. The Institute of Physics, in its 2012 report It's Different for Girls, reported that girls in single-sex schools were more likely to continue with physics after GCSE than girls in co-ed schools. Many co-ed schools now work deliberately on this, so ask any school how many girls take A-level physics and further maths, and how many boys take languages, English and creative subjects.

What the research does not show is that one model is right for every child. Nor does it settle claims about confidence, wellbeing or "distraction" either way; those are harder to measure, and advocates on both sides tend to cite the studies that suit them. Associations representing girls' schools and co-ed schools both publish arguments for their model, and it is worth reading them as advocacy rather than as neutral research.

What matters more than the label

The factors that most often decide whether a school works for a child are ones that cut across the single-sex and co-ed divide:

• Teaching quality and value added. Look at how pupils progress, not just where they finish. See our exam results guide for how to read results fairly.
• Pastoral culture. How the school handles friendship problems, online life, anxiety and behaviour matters far more to day-to-day happiness. Our pastoral care guide has questions to ask.
• Peer group and size. A small co-ed school and a large girls' school may feel more different from each other than the labels suggest.
• Breadth of opportunity. Sport, music, drama, clubs and trips. Single-sex schools sometimes offer a broader range of sports to their pupils; co-ed schools sometimes offer larger and more varied casts, choirs and teams. Check rather than assume.
• Learning needs. If your child has SEND, the quality of learning support will matter more than the gender mix. If they may need extra time or other support in exams, read our exam access arrangements guide.

Practical options between the two

The choice is not always binary. UK independent schools offer several hybrid models:

• Co-ed sixth forms. A number of schools teach boys or girls separately up to GCSE and then admit both into the sixth form. This is common enough that a "boys' school" or "girls' school" label on a directory can understate the mix in Years 12 and 13. Check the entry points and the sixth-form make-up for each school.
• Diamond schools. A diamond model educates pupils together in the prep years, separately from roughly 11 to 16, and together again in the sixth form, usually on one site under one leadership. Only a handful of UK schools use it, so check each school's current structure.
• Partner or twinned schools. Some boys' and girls' schools are separate institutions that share a foundation, a site or neighbouring sites, and run joint activities, trips, drama, music or sixth-form teaching.
• Co-ed prep, single-sex senior. Many families use a co-ed prep school and then choose a single-sex or co-ed senior school at 11+ or 13+.
• Schools in transition. Several historically single-sex schools have become fully co-educational in recent years, and more may follow. If a school is changing, ask how the transition is being managed, what the gender balance is in each year group and how facilities and pastoral structures are adapting.

Family logistics

The practical questions often settle the decision:

• Siblings. Families with a son and a daughter often value having both children in one school, one set of term dates and one journey. Diamond and partner schools can offer some of that while keeping single-sex teaching.
• Commute. A shorter, simpler journey is worth a lot over seven years. A long commute to a single-sex school that looks marginally better on paper may not be a good trade.
• Entry points and timing. Single-sex and co-ed schools in the same area may test at different ages (for example 11+ versus 13+). See our 11+ guide for how entry points and registration deadlines work.
• Fees and bursaries. Compare the full cost, including extras, and check bursary availability early. See our fees guide and bursaries guide.

Questions to ask on an open day

Use the open day to test how the school's model works in practice, not how it is described in the prospectus.

For single-sex schools

• How do pupils mix with the opposite sex through clubs, trips, drama, music, debating or joint sixth-form teaching?
• How do you prepare pupils for mixed university and workplace settings?
• What proportion of pupils take subjects that are less common for their sex, such as physics for girls or languages for boys?
• If there is a co-ed sixth form, how many pupils join at 16 and how are they integrated?

For co-ed schools

• What is the actual gender balance in each year group, and in the year your child would join?
• How do you make sure girls and boys both participate fully in class discussion, leadership roles and less-typical subjects?
• How do you handle sexual harassment, online behaviour and relationships education, and how are concerns reported?
• Are sports and activities genuinely open to everyone, and are teams and fixtures offered at similar levels?

For any school

• Can we see value-added or progress data rather than only headline results?
• How do you support a child who is shy, anxious or not in the popular group?
• What does a typical week look like for a pupil like mine?

How to use our data

You can browse the schools behind the figures directly:

• Girls' schools and girls' schools in London
• Boys' schools and boys' schools in London
• Co-ed schools and co-ed schools in London

Each school profile shows its entry points, published fees and, where we have enough data, its Houseroom Index score. Treat the Index as one input: it rewards strong outcomes, which partly reflect intake, so compare schools with similar entry requirements where you can.

Sources and method

• Houseroom school directory: counts, medians and coverage are calculated automatically from the schools we list, excluding archived records, and refresh at least daily. Our coverage is fullest in London; outside London we list fewer schools, weighted towards the better-known ones, so those rows describe our listings rather than every independent school. "London" means a school in one of the 33 Greater London local authorities. Medians are shown only where at least five schools have the data. Day fees are the lowest published annual day fee we hold; figures outside a plausible annual range are excluded as likely data errors.
• Pahlke, E., Hyde, J. S. and Allison, C. M. (2014), "The effects of single-sex compared with coeducational schooling on students' performance and attitudes: a meta-analysis", Psychological Bulletin: doi.org/10.1037/a0035740.
• OECD, Programme for International Student Assessment (PISA): oecd.org.
• Sullivan, A., Joshi, H. and Leonard, D. (2010), "Single-sex schooling and academic attainment at school and through the lifecourse", American Educational Research Journal: doi.org/10.3102/0002831209350106.
• Institute of Physics (2012), It's Different for Girls: the influence of schools.

This guide is general information to help you compare schools. It is not a recommendation for or against any school or model.