Talkinpeace said "Most free schools do not take SEN kids"
Show me a free school admissions policy that excludes them Talkinpeace!
Children with SEN statements that name the school will be prioritised for entry. It's illegal to do otherwise.
However I suspect most authors of SEN statements, and parents of SEN children, would want a school to be up and running for a while, with a demonstrable track record, before naming it as their school of choice. That's why the numbers are low. Because they're new schools, not becasue they're free schools.