High school cross running coach has detailed plan for students

My son's high school cross country coach handed out day-to-day training plan for two months at a time and the kids adhered to it strictly.  Weekly mileage would be at least 35-40 miles plus conditioning and core. They do this all year long, not just the cross country season from August to October.  The coach also handed out recovery/stretch/injury prevention instructions and kids followed along too. With this kinds of training for three years now, my kid and his running friends go out to run every day no matter if it is raining/snowing/windy/hot weather without parents' reminder.  So I agree running is a life long sport and you  have to keep it up. With younger teenagers, half marathon is quite appropriate but I discourage my son to try full marathon or even longer ones now since there are quite a lot of people in town doing the extreme/ultra running and they do them on regular basis.