I teach Alevel and have a bit of experience of local schools and think it really depends on the quality of teaching at her current school. She should look carefully at the results for the subjects she is interested in and find out about things like class sizes, resources etc. She should also check whether the school she is at and the one's she's interested in can offer the combination of subjects she would like. If a lot of students are planning to leave for other schools then there may be a good reason for this. Is the sixth form very new or small? Did it get poor results recently? It is really important to be somewhere with a high quality of teaching staff with experience in the courses she wants to do and also experience in applying for higher education. Both Charter and college will offer this, but it depends a bit on what subjects she wants to do and her personality which would be best for her. Charter will offer predominantly traditional academic subjects (although I believe they do some btec courses and more 'modern' Alevel courses like media), whereas the college will have a much wider range of courses. The college will also have a much more 'grown-up' approach than school sixth forms, with more independence and freedom, which sounds appealing but of course whether that is a good thing depends on your daughter!