There are some FANTASTIC FREE training resources you could use to build a complete training plan for your team.
Note: All links are fixed!
I've never seen a free resource this detailed on how to construct a season. Rubio states this is for elite runners, but high school coaches can use the same concepts, but scale back. The worst thing coaches of developmental runners can do is blindly copy what the elites are doing. Use the ideas, but think of it in terms of, "This is what I want my runners to be doing in 4 years, so what can I do now that can prepare them for this."
These aren't workouts, but rather the rationale as to why distance runners will benefit from ancillary training. If all you're having your kids do is run, then you're going to end up with problems. Read this. It's important.
If you want some ideas on what a balanced weight training program includes, this article from Team USA is pretty good. There's a balance of different lifting movements in each session (push, pull, squat, hinge, etc.).
If you're a distance coach, you've likely already seen Coach Jay's free video library, but it's worth showing again. I love the SAM (Strength & Mobility) routines the best. Add these on days you're not in the weight room.