I mentored teaching students from my second year of teaching, in the seven different authorities I worked for, with students trained at Training Colleges 3 year courses, B.Eds, PGCE, from the mature students college to distance learning (so much help given) and and I never, ever heard of any student passing a Teacher Training course and being awarded a certificate to teach pupils only in small groups. Full-class teaching was an essential part of every course and had to be achieved, without support and adjustment , to achieve the qualification.
No Headteacher would appoint a teacher who was not competent in full-class teaching, for what ever age. The idea that a teacher who could not deliver to a class of adults would somehow be able to cope with primary age pupils, and vice versa, is nonsense.