Diamond schools

Diamond school, diamond model, diamond shape and diamond structure are similar terms that apply to a type of independent school in the UK that combines both single-sex and coeducational teaching in the same organisation. Typically, the establishment will be all-through, often with a nursery setting, and boys and girls are taught together until the age of 11, separately from 11-16, before coming back together again in a joint sixth form.

Diamond schools are often the product of the merger of a boys' and a girls' school, thus it is possible that at KS3 and KS4 girls and boys can be taught separately on different sites. It is a common feature that boys and girls combine outside the classroom in activities for academic trips and visits and in some co-curricular activities, such as choirs, orchestras and the Duke of Edinburgh Award scheme.

Diamond schools in the UK independent sector include:

Teesside High School adopted the diamond model in 2005 but became fully coeducational in 2015.

...
Wikipedia