No, BASIS does not exactly offer a formal mentorship program. The schools do hire teaching assistants in varying numbers each school term. However, in the two years I worked with BASIS I rarely, if ever, saw any people from the TA program get hired on as teachers, and none of the teachers at my campus had been TA’s. The vast majority (if not all) of the faculty are hired as teachers from the beginning. It is not especially unusual to get hired on with no teaching experience at all, although it is very helpful.