Joining RAF at 16

I'm hoping to join the RAF at 16 as my post 16 option as a mech. I've called and messaged the RAF and they have been little help. My first question is this possible my OC at cadets told me it was 17 and a half but he's not the best at this stuff. When does it start? Do I apply to it like I do my A levels? At Halton do they treat you differently?