[APG]

NCAA Rule 7-3-2 e:

ARTICLE 2. A forward pass is illegal:
e. If thrown from in or behind the neutral zone after a ball carrier in possession of the ball has gone beyond the neutral zone
Penalty: 5 yard penalty from spot of foul and loss of down

NFL Rule 8-1-2 Item 1 (c):

Any other forward pass by either team is illegal and is a foul by the passing team, including the following:
(c) A forward pass thrown after the ball has crossed the line of scrimmage and has returned behind it
Penalty: Loss of five yards


I'm not sure about NFHS, so I'm sure someone will come along and give you the proper ruling.