[mikesears]

What you are asking about is blocks below the waist. I have an NFL rulebook and officiate in a semi-pro league using NFL rules. It kind of funny (and a little scary) watching a high school/college official try to learn a new set of rules. I'm still unclear on a lot of things.

From my limited understanding of the rulebook, the NFL allows blocks below the waist anywhere on the field during a scimmage down. EXCEPTION: The only time they are NOT allowed is after an interception, after the ball has been kicked (as in a punt or field goal), or during a free kick down.

As long as the block isn't a clip (block below the waist from behind), I believe it is legal. You may want to wait for a second opinion on this.

Sounds like you have high school referees who are unfamiliar with the NFL rulebook.