You can ask "What are schools for?", and you can ask "What is education?", but to ask what education is for is rather like asking what happiness is for: both are ends in themselves.
Schools can be for various things, of which education is one; others include training in key skills, preparation for work, pastoral care, and socialisation. This is not just pedantry.
To suggest that education is "for" anything invites those in power to regard education in purely instrumental terms and to forego the more difficult task of analysing what it means to be an educated person.
It is perfectly possible to conceive of schools which are efficient in training and instruction and produce citizens who are law-abiding and employable, but whose students are not educated. Indeed, this is the danger of endless target-setting, box-ticking and testing.
Fortunately, most schools manage to educate their students in spite of these pressures, but it is not easy.
Dr Jim Docking Winding Bromley Old Road Buckland, Surrey