You can say both.

you can say both, but it is silly to say the second. To say 'you have done something' is to connote the indefinite past. In this case both you and your teacher know exactly what it is you should have read and when you should have read it, so you use the definite past. ex: I have skydived (perhaps several years ago, or perhaps just yesterday). I skydived yesterday (very certain).

Sorry,I forgot to read this.