I believe that they shouldn't play tackle until 7th grade. And then they should all play rugby.
This: I love football, but Rugby is a superior sport.
1 To a poster upthread: It's not so much the risk of catastrophic injury as the cumulative effect that mainifests itself years down the road. Some researchers say children and adolescent brains are more susceptible to this type of damage.
2 Football is unlike baseball, golf, etc in that fine motor skills are less of a factor, and those that are don't apply to blocking and tackling. By the time he gets to high school, a kid who starts playing tackle football at age 8 has little, if any, skill advantage over a kid who starts playing in middle school. You can learn to block and tackle in a few months. It's not like learning to hit a curve ball. I played HS football with several guys who went on to college ball. Two of them made it to the NFL. All of them started playing in 7th grade. The delay didn't hinder them one bit.
The responses on this thread are predictable, but this isn't much of a big deal. Kids that age oughtn't be playing organized sports anyway, IYAM. They should be playing pickup games in the front yard. Organized sports leagues, and especially things like travel ball, are mostly about the parents ego.