Hill, named the game's most valuable offensive player, scored two rushing touchdowns and two passing and accounted for 345 total yards from scrimmage for the Dragons (16-0), who won the school's eighth state football championship in front of 42,896 at Cowboys Stadium.
Hill, a junior, was 19-of-24 passing for 229 yards. Davis, named the game's most valuable defensive player, had eight tackles and was part of a key sack of Hurricanes quarterback Bralon Addison, forcing a punt on what turned out to be Hightower's last possession.
Sabian Holmes had 138 yards on 11 catches and a touchdown for Carroll.
Addison, with 184 yards rushing, scored two touchdowns -- one on an 80-yard run -- for Fort Bend Hightower (13-3), which was making its second championship-game appearance.
The Hurricanes held a nine-point lead when Hill found Holmes on a 59-yard touchdown pass over the middle to cut Hightower's edge to 23-21.
The Dragons went ahead for the first time since an early 3-0 lead on Hill's 25-yard scoring strike to Corey Kemp with 2:49 left in the third quarter.
Addison also had a touchdown pass to Ryan Nelson. Jaquinn Henderson had a 5-yard touchdown run for the Hurricanes' first score.