If you don't pay enough, the most qualified won't apply. Instead you'll fill positions with people who think that contract hours are optional, work should never be taken home, and because they don't want to do any additional work they sit the kids down for a few hours of Bill Nye every week.
Anyone who actually is doing their job with any degree of competency will either quickly leave the field or will continue despite the unfairness at great personal sacrifice.
It's so ironic that LDS people place so much importance on the value of children to society and the value of education, yet do so little to support basic education.