To answer a few questions:
I don't know if having 5 under 5:10/2:20 and 19 under 2:35 is good or if they are all capable of 4:50/2:10 and I am doing them a disservice? I do the best I can and try to give them the best situation possible.
We do not do form drills so it takes 0% of the pie. Our school gives kids 3-4 hours of homework a night and I try to take no more than 90 minutes a day, although weights days (Tue/Thur/Sun) we go about 2:00. Form is something we review and talk about in every workout and run. I teach a small understride. It feels far too short for most at the beginning. However, it forces a dorsi-flexed ankle and landing on the mid-foot, off the heels. We progress to over 180 spm quickly when most HS beginners are 150-160 at best. Over time, with many steps, hills, and weights the stride length naturally lengthens without eroding turnover. Our form and turnover as a whole is noticeably different than most of our opponents. That is "my" definition of better form; high stride rate, dorsi-flexed ankle, and off the heels.
On the step & surge workouts, we emphasize these and keeping hips "high" to avoid that in the sand feeling at the end of an 800. Notice how many girls hips tend to angle back (like sitting) when tired. We try to avoid this happening in all workouts, especially when tired. I also wait at the top of the steps in some reps, put my hand in the middle of their lower back, and push them to get turnover restored get them doing what is asked. As soon as they get over the hump of getting going, good things form-wise take place.
My experience is that overstriding is a contributor to injuries as someone said as well as below average performance in the majority compared to mid-foot striders. I have had only 5 major injuries in over 25 years of coaching although I have one now to a 5:00 girl.