Any danger of revealing where this school is? Full flap when turning base leg to final approach is going to inevitably lead to someone spinning in, simple as that.
Have you asked your CFI why he insists upon this ludicriously dangerous SOP?
I teach lowering full flap once sure of making the runway. You will look a bit silly landing short of the runway with full flap on the day the donkey dies 1 mile out.... seen it happen before.
VFE.