I would offer an alternative view that it will be very difficult if not impossible to adequately teach and supervise high school athletes in the weight room with less than one hour per week. I would think that the gains would be negligible at best.
I would advise using alternative strength training methods such as prisoner squats holding kettle balls or in place jumps with weight vests. You can work a large number of kids in a short period of time. The technical demands of the activity are lower and therefore easier to teach and supervise. And given a 12 week season, the results should not be much different than conventional weight training for that age group.
my 2 cents