Blackfoot dominates the first half and takes a 26-0 lead over Skyview at the break.
Firth is trailing 15-12 at Declo after the third quarter.
In other action:
Hillcrest 30, Columbia 6 in the 2nd
Eagle 31, Lake City 0 in the 2nd
Highland 35, Meridian 18 in the 4th
Marsh Valley 68, Kimberly 37 Final