DC-BOOK

The learning curves of 8-9's is dependent upon two things. First, are you allowed to be on the field with them? If so, you can teach them ANYTHING. If not, then you need to organize a scrimmage with another team (or, if you have 22 players, against your own offense) and then be on the field with them. Say 2-3 such scrimmages and, again, they'll play like 12's (At least the 9's - Some of the 8's will move very slowly and unsurely as you call different defenses even if they know what to do). Now let's say you can't be on the field and you haven't got 22 guys or you can't arrange a scrimmage. You can still teach them two defenses. In fact, you can teach them 3 or 4. Here's how. With the defense standing in front of you and you standing behind a football on the ground, simply call out the defense you want them in. They now have to get themselves properly aligned on the ball. They'll move slow the first 2-3 times you call them but then they'll have it mastered. If you do this, start out with just two defenses. That's a real simple learn because they're either in one position or the other. The next night add a third - but never more than four. If you're going to use this last technique you need to make certain that, at this level, a new defense creates a position change only but NOT an assignment change. A DT or DE should play the same way in all your defenses. In all these systems, you can take your smartest kids and place them in charge of your dumbest kids. Thus, the smart kid moves the dumb one plus himself. You should have at least 2 kids that are smart enough to move others which is a good thing because you'll probably also have two kids too dumb to move themselves.
The simplest combination of defenses to move 8-9's in and out of are 6-1, 5-2, and 8-3 (8 man Gap). The 6-1 is useful because many coaches try and have their center block the MLBer in a 6-1, which can't be done. The 5-2 is a useful training defense to teach inside LBers to shed blocks and follow their man. If you can teach pursuit angles, the 5-2 is great. Both defenses use Cover 2 so your deep and outside coverage plus DE play are the same in both defenses. That keeps things simple. 8-3 is useful as a goal line defense. As the season progresses and the kids learn the first three, you can add a "Split 6" about game three. You're now in the playoffs - And probably undefeated!