I gotta be honest. 5-6 year olds can play some pretty amazing football if you just give them the right tools and set a high bar, all along making sure they have fun. I've seen kids this age learn quickly and make some tremendously athletic and intelligent plays. In terms of the best defense in a 5/5... I personally think its the V. I tried other formations and my teams always gave up 2-3 touchdowns per game. This past season we hardly gave up first downs. Obviously the V looks like a kid over Center, 2 LBs and then 2 DBs a few steps back. For it to work, you need to teach the following: 1. The kid over Center (lets just call it a NG) has to be very alert, aggressive and a great flag puller. In our league the QB can't run so our NG has to disrupt plays in the backfield as soon as they happen. He doesn't have to be a super fast kid- just alert and aggressive. Sometimes this is a good spot for a big kid who maybe lacks a lot of lateral quickness. 2. The 2 DBs can actually be weaker flag pullers provided they are good at defending the pass. Their job on runs is simple. Get up the field, cut off the runner, protect the sideline and push the runners back towards the middle of the field. I had 2 DBs play great this season and between the 2 of them combined they probably only grabbed a handful of flags. Let the LBs get the glory. 3. Your 2 LBs need to be both great flag pullers and very good athletes. If the play goes right, the right LB attacks and the left LB drops back to protect against misdirection. Same holds true the opposite side. (Actually, the V becomes a L when the play goes right and a backward L when the play goes left so the defense never loses contain). The one weakness of the V is a deep pass over the middle. This is where you need to be able to drop at least one of the LBs back as a safety. I typically keep the faster LB, move him to the weaker DB's side and then take the other LB and put him back 3-4 yards. Realistically, kids this age won't throw more than 15-20 yards max so that LB should still be able to run up and attack a run play. Try it if you wish. . If you do, stick with it and you'll see the results. It takes time but once the kids get it they dominate and it usually shuts down bigger, faster kids as well. We played a great running team and a great passing team back-to-back in the playoffs and our kids allowed a total of 2 offensive touchdowns, 5 first downs and blew the teams out. Good luck.