I've not flown a C152 more than once, so can't comment on the aprticular aircraft, but I recently heard from an instructor who teaches on PA28's that they usually have students only use 2 stages of flap instead of the usual full flap as it gives better airspeed margins over the stall, which may be required in gusty conditions (the instructor was at a gusty island location!) and generally more room for error in this dept. for early stage students. They later get them using full flap. I guess its down to the instructors preference - but this may be whats behind the different approaches? Why not ask over on the
Flying Instructors forum?