I think in WW2 you had four phases of training each with completely different aircraft.
Primary training- Piper Cubs , PT-19, etc might be performed by civilian flight schools,
Basic training- Bt-13, BT-9
Advanced training- Texans,
Transition training- P-39, early model P-40, P-51s,
And that's just a partial list for the Army, the Navy had it's own program with some of it's own unique aircraft. There's also navigation training aircraft, bombadier trainers, etc. Then there's all the other countries flight training programs, you can't just consider a token few aircraft.
A lot of unsung heros out there.