Yes, in Cedar Rapids/Iowa City, some league start tackle football in 3rd grade. For the MYFA in Cedar Rapids, it starts at 4th Grade. They do have weight limits on ball carriers and how far defenders can be from the line of scrimmage, but you still get some pretty good pops happening on the field.
I started playing football in third grade, age eight. My best friend Randy and I stood in line to sign up with the two-team peewee league. Little did we know that the men at the table signing us up assigned one guy to the Colts, the next guy to the Jets. My Dad and Randy's Dad went to all of our six games, their sons on opposite teams. We beat the Jets five times out of six, thanks to the randomness of the line we were standing in.
Pretty sure I suffered my first (probable) concussion two years later when I was ten and playing for the Redskins. There were four teams by that time. In a practice I collided helmet to helmet with Mike Smith. It was excruciating pain in the head like I had never felt before. I remember nothing after that, not even Dad picking me up from practice and driving me home. Dad and I were told I was wobbly and Coach took me by the arm and had me sit down for the rest of practice.
I know, CSB. I loved playing football when I was eight and ten, and the next seven years. it was a lot more fun than school. If I had it to do over again I would not have missed it for the world.