[TheStickyBandit]

Depends on the personnel of the team but I would prefer to run a 3-4. Your outside linebackers may be the most critical positions in this scheme because ideally you would want them to be the most versatile players on the field. In a perfect scenario, they would be able to set the edge to stop the run, provide pressure on the QB when needed, but also be athletic enough to guard slot receivers or at least drop into zone coverage for pass defense. 

I am a fan of mixing coverages up because all to often teams will set in the same coverage all game and then they get burnt in the second half after the coaches have coached the QB up at halftime on what to key in on when making reads. Mixing coverages up alone will keep the majority of highschool QB's confused. I would run a mix of cover 0 and cover 3 depending on the opponent, the down, and the distance to go. 

Defense is fun and defense in highschool should be especially fun so I am a fan of being aggressive and letting linebackers and secondary players pin their ears back and blitz from time to time.