Grabbing the Helmets??

[rockyroad]

I am a long-time basketball official, and post over on the basketball side , but am new to football stuff. My oldest son decided to play as a freshman this year, so I'm learning as we go...my question and scenario: last night's JV game, the defensive linemen would (about every third play) not even go into a stance (3 or 4 pt), and as the ball was snapped, they would grab the offensive linemen by the back of the helmets and shove their heads down...what - if anything - should the penalty have been??? The crerw (3-person crew) was not calling anything until one of the fans (about 20 of us there) started hollering about lawsuits (no, it was not me) and then the crew "conferenced" and told the coaches of the other team to have the players stop doing that or they would penalize them - so it ended...my kid woke up with a pretty stiff neck this morning, tho...thanks for any info.