Do girls really do best in single-sex schools? Is co-ed best for boys? Academic success, it seems, has more to do with the culture of the school than the gender of its pupils.

There is a popular notion that single-sex education is better for students, and particularly for girls. The extensive body of research into the relative merits of single-sex and co-education doesn't come down conclusively on either side, but this perception informs the choices of many Irish parents.

More Irish girls attend single-sex schools than do Irish boys, and the intake of boys to co-educational primary schools has tended to outweigh the intake of girls. This may be about to change, according to Paul Rowe of Educate Together.

"Later this month we will release the results of an Educate Together school-wide survey which will show that the gender gap at Junior Infant level has narrowed to almost nothing. New parents are increasingly comfortable with sending girls to co-ed schools."

This may be the case at primary level, but life gets complicated at secondary. First-year students are embarking on two of the more stressful stages of life: the State exam cycle and puberty. There are 473 co-ed secondary schools in Ireland, 152 all-girls schools and 118 all-boys schools.

It is widely held that girls have a civilising effect on boys, while boys out-shout and overshadow girls in the classroom. Are girls better off in the complacent sisterhood of the convent school away from rumbustious teenage boys jostling for position? "Gender is not a 'pure' attribute operating independently of other characteristics," says UCD's Kathleen Lynch, co-author of Equality and Power in Schools.

"The social class, racial, religious or ethnic identity of students, as well as other factors such as school traditions, can all play a key role in determining the culture within the organisation, and the experiences of pupils and their parents." Kathleen Lynch and co-author Anne Lodge spent two years observing the classroom dynamics of 12 Irish schools. They concluded that school culture, streaming, socio-economic profile, entrance criteria and parental involvement all contribute to the academic outcomes of students.

However, Lynch did observe certain trends peculiar to single-sex education. According to her, all-girls schools tend to impose strict rules in relation to appearance and demeanour. Every former student of an all-girls school will recall rows in the corridor over personal interpretations of the school uniform. According to Lynch, this is not a common concern in all-boys or co-ed schools.

Lynch and Lodge observed that classes in all-girls schools were more focused and spent more class time "on task" than did all-boys schools or co-ed schools, where more time was taken up with social interaction and discipline. Girls in single-sex schools in Ireland are far more likely to complain of academic pressure and stress.

The scene is quite different in the average all-boys school. "Boys' schools [and classes] represent spaces where internal gender hierarchies and identities can become exaggerated," says Lynch. "In all-boys' schools, sporting prowess tends to generate status and recognition." In the four boys' schools that Lynch observed, classes tended to be more active, with greater interaction between students and teachers (not all of it positive).

The power of the peer group was also more obvious among boys. In the co-ed schools the authors found as much diversity within the group as beyond it. Some co-eds were very committed to balancing the power between girls and boys in the schools, whereas in others, inequality went unchecked.

Overall, boys in the co-ed schools studied were more likely to get teacher attention and dominate public discourse in the classroom, but in a significant minority of cases, girls were running the show. Overall, the culture of the co-ed tended to be closer to the culture of the all-boys school, with more relaxed relationships between staff and students. Of the three groups, the all-girls schools emerged as having the most academic focus.

However, Lynch is eager to point out that on average, single-sex schools are more middle-class in their intake than are co-educational schools. Parents with high ambitions for their daughters may be more likely to choose a single-sex school because of its reputation. Parental ambition and affluence may be more important coefficients in the success of a student than the gender mix in the classroom.

Emer Smyth of the ESRI agrees the gender mix in the school ranks low on the list of factors contributing to a student's success.

"There are a lot of myths circulating about the relative merits of single-sex and co-education," says Smyth, co-author of the 1996 study Co-education and Gender Equality: Exam Performance, Stress and Personal Development. "We conducted a national survey of schools, taking account of all their differences, from gender profile to social class.

Single-sex schools, on average, are more middle-class in intake and tend to draw students of higher initial ability. When we adjusted for social class and prior ability we found no significant different in the academic outcomes of students from single-sex and co-ed schools, in either the Junior or the Leaving Certificate. There was far greater variation between schools of different levels of advantage - that's the real issue."

Mother of three Barbara Johnston, a spokeswoman for a Catholic parents' group, has had experience of all three types of school. One of her sons attended an all-boys school, the other went to a co-ed, and her daughter left an all-girls school for a co-ed.

"While all the surveys seem to show that girls do better in single-sex education, I think that has a lot to do with the expectations and social profiles of the parents.

In terms of social adjustment, co-education has been the better option for my family. My daughter left a single-sex school to go to a co-ed and she's much happier there. She experienced a high level of what's now described 'relationship bullying' in an all-girl environment. She also experienced a lot of academic pressure."

It's a tough choice for parents to make. Some students are better suited to a single-sex environment while others need an education experience that is closer to the real world.

Over the coming years the choice may become less available as more boys' and girls' schools come under pressure from falling student numbers, and amalgamate to form co-ed community schools.

In the meantime, parents should rest assured that the culture of the school and the involvement of the parents are more important to a student than who sits beside them in class.