There are several special schools available where the model is full time 1:1 for each and every child.
Generally, the model works well, and the children there make more progress (real, well documented progress, not hothoused tutored rote learning that cannot e applied elsewhere) than was ever expected from them at previous educational establishments.
Full time 1:1 does not mean full time dependence, btw, and it is very and narrow minded (although typical of most ms teachers, ime) to think it does.