A few rule differences:
1) 15-yards is required for a first down
2) All players are eligible receivers
3) There must be at least one exchange of the football in the backfield before the ball can be advanced by rushing past the line of scrimmage.
4) All kicking PAT attempts are worth 2 points, and a rush/pass PAT attempt is worth 1 point. Field goals are worth 4 points
5) Overtime possessions are started from the 15-yard line, as opposed to the 10-yard line at other levels of high school FB