Guys, all of these rules involving fouls on scoring plays changed in 2010 and were modified again in 2011. These fouls can carryover - it happens all the time.
Straight out of the 2011 rule book:
ART. 2 . . . If an opponent of the scoring team commits a foul (other than
unsportsmanlike conduct on a nonplayer foul) during a down in which a touchdown
is scored and there was not a change in possession during the down, A
may accept the results of the play and choose enforcement of the penalty:
a. On the try, or
b. On the subsequent kickoff.
ART. 3 . . . If an opponent of the scoring team commits a foul (other than
unsportsmanslike conduct on a nonplayer foul) during a down in which a touchPage
65 2011 NFHS Football Rules Rule 8-3
down is scored and there was a change of possession during the down, and such
foul occurs after the change of possession, the scoring team may accept the
results of the play and choose enforcement of the penalty:
a. On the try, or
b. On the subsequent kickoff.
ART. 4 . . . If either team commits an unsportsmanlike conduct or a nonplayer
foul during a down in which a touchdown is scored, the opponent may accept
the results of the play and choose enforcement of the penalty:
a. On the try, or
b. On the subsequent kickoff.
ART. 5. . . If after a down in which a touchdown is scored, and prior to the initial
ready-for-play signal for the try, either team commits any foul for which the
basic spot is the succeeding spot, the offended team may accept the penalty and
choose enforcement of the penalty:
a. On the try, or
b. On the subsequent kickoff.