I totally agree with Honest Frank!
With flaps out, the PA28 will take off in no-time. One thing is that I don't want the student to be looking for the flap handle at Vr, but another thing is that I don't want any flap retraction shortly after take-off, unless we're cleared for touch'n go...
You also want to be sure that the flaps actually come up before lifting off again!
Flaps first, then power.