Idaho must have over 75... Arizona has hundreds, as well as Washington and Oregon... And don't forget California.
If 2 or 3 if the top 5 kids from the utah schools go to byu, and 1 or 2 of the Idaho kids choose byu, then how much of a stretch is it to get to 1200?
Think of all those rural, small high schools there are all over the west. Is it not plausible that a mormon kid can sneak into the top 5 of a class with 50 students?
Seems like a reasonable percentage!