All in a flap
BEagle, I agree, but.....
This absolute idea that only full flap is acceptable - to me is un-acceptable. Unless the POH forbids (the PA28 manual has nothing to say on it) then with good reason use the configuration that best suits the aim of the exercise but just the same fly the correct speeds and allow nothing else. If the speeds not correct, GO AROUND!
Stall speeds are shown in the POH for level flight and differing angles of bank. From memory the stall speed for the PA28 is no higher for 25 degrees of flap than when the max flap 40 degrees is used. The final 15 degrees is not a critical setting therefore and there is no discernable pitch change for the student to learn, when applied.
BEagle note 4 and earlier comments;
One of the issues not addressed is the amount of appalling flat landings anyone can witness with students/PPLs landing the PA28 series. Partly, I blame this on the absolute insistance of the use of full flap during training, whatever! One problem with the PA28 is the limit in pitch control, at below landing speeds, from the stabilator. This is different from the greater sensitivity of a conventional fixed tailplane/elevator. Even at taxy speeds you can pitch a Cessna. Should the student retard power a mite too early or round out a tad too high they will almost always land flat at best or even worse on the nose wheel. Landing can be something like a belly flop and you can get away with it although not with me and i'm certain not with you. Allowing this will only encourages the wrong image to fester in the students head. If allowed they will probably be quite pleased just the same and not grasp the reason why you complain afterward. The PA28 is not so keen to porpoise unlike many other types such as the Cessna series and lessons therefore may not be learned as they might.
Certainly during the early sessions in the circuit landing with 25 degrees means speed is not lost so rapidly and allows the student more time to observe and experiment during the hold-off and the instructor more time to coach them through. Should they 'balloon', whats the problem with that, the answer is simple, it is to go around - i'm sure we all agree - and you cannot practise that too much.
With the landing attitude thoroughly learned then introduce max flap and the factors that go along with that. However, I would certainly require the student to be competent at max flap landing on the mains, prior to solo.
Approaching using the correct speeds and landing on the main wheels is by far the most important rule to foster. Second is the willingness to go around. Thirdly, well, some aeroplanes don't have flaps.