My wife just received her UK passport she has lived in Canada all her?
I think you need to explore the UK visas web site. We would need more information to establish whether your son is entitled to British citizenship (unlikely) but he is probably eligible for a visa to spend time living and working in the UK as the descendant of a British citizen. And what do you mean by school? To us, schools are for children aged 5 to about 19. These schools are available to any child who lives nearby, so long as there is a place available, at zero cost. If you meant university, then anyone from anywhere in the world is free to pay the tuition fee and come to study with a student visa. We do have a system of grants and loans, along with reduced tuition fees, for Home and EU students, but eligibility for this depends on having lived with the EU for at least three years immediately before the course starts. (Even British young people who spend time abroad between school and university may be caught out by this.)