If you aren't enforcing the screening rules correctly, then you are contributing to the rough play that the NFHS is striving to reduce.
Can you provide a reason why one shouldn't penalize an illegal back screen that failed to allow the opponent one step backwards prior to contact?
PS The NFHS considers the visual field of a player to be anything to his front or sides, only behind him is not part of it. It says so right there in the rules:
4-40-3 . . . When screening a stationary opponent from the front or side
(within the visual field), the screener may be anywhere short of contact.
NOTE: the red text is NEW. It was not in the 2006-07 rules book. Yet another unannounced editorial change! 