When I was in high school (god, that makes me sound old) our best guys would do 50 max per week (the varsity team would avg low 16's). Our coaches believed in preparing us to run in college and get ready to handle bigger volumes. It was funny to watch our main rival do 70 mpw in the summer, smoke everybody early on, then they all burn out by conference/district/states. HS ain't the time for glory, but some coaches just want titles and records. Unless you've got Andrew Hunter, there's no need for it. I feel bad for those kids.
That is not at all representative of the AVERAGE high school team. Some high school teams don't run 50 miles all season.