The chance to have the best of both worlds, by creating a fully co-educational preparatory school and sixth form, but retaining the single-sex senior schools from 11 to 16, seemed attractive - partly so that neither school lost its identity and partly since research suggests this model can be advantageous to both sexes.

We decided to restructure the traditional 13-18 public school house system by separating sixth-form students into co-educational day houses. Then we extended the senior boys’ houses down the age range to 11, while retaining our 13-plus entry from other preparatory schools and, at the same time, established our co-educational preparatory school to include the 10-year-olds who had already transferred into the junior part of the senior school. This “diamond” model seemed to meet our requirements.

The changes fell into place quickly for the pupils as we briefed staff, parents and feeder schools. Sixteen-year-olds became house officers in the 11-16 senior school, while the sixth form developed more of a mature, college ethos as students focused on their options for higher education.

Pupils still make their A-level subject choices in their single-sex Year 11 environment, which mitigates the traditional gender skew (for example, in languages or physics) apparent in some co-educational schools.

The major change at 16 from single-sex to co-educational classes now coincides with the academic shift into more advanced study, and raises student expectations. As one student says: “I’m enjoying the co-ed sixth form: it feels more like a university.” Meanwhile, children at the other end of the age range have the benefit of an additional year in key stage 2 to consolidate their numeracy and literacy skills before transferring at 11-plus into the larger academic senior school.

What has been the impact on teaching and learning? Most staff had taught both sexes and adapted confidently; those who assumed the same lesson plans would be appropriate for girls or boys found the class had either finished the work halfway through the time allocated or had failed to cover all the key points before the bell. Some less familiar with the questioning style of boys had to adapt their classroom management and others had to learn how to encourage the girls to engage more actively in lessons. It gave staff the chance to reappraise their teaching styles.

As for learning, the induction into co-educational sixth-form study demonstrated the importance of understanding gender issues. Sometimes, in the first few A-level lessons, the boys actively engaged with the ideas under discussion while the girls wrote copious notes and studiously read the texts. Once the first essay was set, the boys realised they needed to back up personal opinion with knowledge of others’ views, by which time the girls had learned enough to realise that the boys’ opinions voiced in class were not necessarily reliable and felt confident to challenge them. The two groups quickly learned much from each other about good practice to help them progress confidently into higher education.

Berkhamsted came through the changes with flying colours. Staff have made real strides in professional development, academic progress and pastoral care, and parents have seen the benefits. Prospective families are delighted to find they can have single-sex and co-education under one roof at the various stages in their children’s development. Most importantly, the students’ success and commitment to their school have made it all worthwhile.

Dr Priscilla Chadwick is principal of Berkhamsted Collegiate school and next year’s chairman of the Headmasters’ and Headmistresses’ Conference