For children, joining a new school can be stressful and it is easier to join with other new pupils. All secondary schools will have principal entry ages - usually 11 or 13 - but may take pupils at other "natural" points related to the curriculum, particularly at 16; some schools will take a flexible approach at taking pupils at other ages; and some (particularly international schools) take pupils at any stage.

Sixteen can be a natural age to change schools after GCSEs. Pupils may be struggling to meet the requirements of their present school's sixth form, be looking for a school where they are treated more like an adult or just fed up and need a change. It can be a good opportunity to look for more appropriate courses (the IB or vocational A-levels). But it is not a universal panacea for everyone: the existing school will know know pupils' strengths and weaknesses and can teach to them; and moving schools can cut badly into short, intense sixth-form courses.