Just a few years ago, one tiny Texas school system decided to try a four-day school week. Now, nearly 50 districts use them. Officials hope the schedule attracts quality teachers and helps retain the rest, as many schools struggle to stay fully staffed. The schedule is still being tested in many schools; but in others, results are in.

In the Athens Independent School District, 75 miles southeast of Dallas, school began Monday. But this year, it's not the usual Monday to Friday schedule.…