I am by no means a professional on the topic, just someone who enjoys reading about running.
You seem to be confused about the running workouts/types of run. Basically, you give your body a stimulus so it can adapt while running. Adaptions can include changes to the aerobic or anaerobic system as well as muscle strength improvement. The aerobic and anaerobic systems are the two systems that power us when we run. It's a little hard to describe but basically aerobic is for long distance runners and aerobic is for sprinters. Middle distance runners train both. Since we are talking about cross country we want to train the aerobic system. We can do that by stimulating the aerobic system effectively. Read more about aerobic conditioning for long distance runners here:
https://runnersconnect.net/running-training-articles/the-importance-of-aerobic-running/
There can be different stimuli such as running itself or cross training.
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There are several different types of running stimuli aka workouts:
The main types of running workouts:
Recovery Run.
Base Run.
Long Run.
Progression Run.
Fartlek.
Hill Repeats.
Tempo Run.
To read more about each of these runs, please go to this link:
http://running.competitor.com/2014/06/training/running-101-the-8-basic-types-of-runs_7984
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Other sorts of stimuli can be called cross training which can include weights, yoga, biking, swimming, etc. Basically you can still work on your aerobic base while not running. This would preferably be with zero impact activities such as the previously mentioned examples.
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Hopefully you understand what your son's coach is doing. He seems to know what he is doing in terms of workout structure. However, the workout with the 100m and 200m repeats is kind of useless to endurance athletes. This workout improves the anaerobic system which is useless to distance runners.
The coach probably wanted to improve the kids' "final kick". However, just doing sprints is ineffective. I would suggest that the coach add strides to the end of each easy or long run. If he wants more a structured workout to improve the kick, I would suggest progression runs, hill sprints, or adding 6-12 200m-400m repeats AT THE END of a easy run. The difference is that instead of doing a short warmup and then sprints, you get to target both the aerobic and anareobic systems instead of just one.
The rest of the week looks fine to me. Just make sure:
-the kids are having fun
-do your core work
-keep easy training days easy and hard training days hard
-always warmup
-try to keep the kids injury free (increase weekly mileage slowly is a good start)
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Hopefully I didn't just ramble and actually help you. Good luck to your son and everyone on the team.