This might be a silly question, but...

[Mike L]

NFHS does not allow any blocks below the waist except in a very limited area for a very limited time.
First, there is a free blocking zone, an 8 yd by 6 yd rectangle centered on the ball at the time of snap.
Second, the blocker must be on the line and in the fbz at time of snap.
Third, the blockee must be on the line and in the fbz at time of snap.
Fourth, the block must occur within the fbz.
And Fifth, the ball must have never left the fbz before the block.