ineligible linemen downfield

I've read in a couple of places online that there is no such thing as an ineligible lineman downfield during a punt in both HS and NCAA (only NFL). Unfortunately, I don't have a NFHS rulebook...can anyone confirm this for me? In my playing days, and now, we always teach the linemen to either count to two or wait til the ball is kicked (presumably to avoid being downfield illegally).

Thanks!