This is clearly the best team that has ever run in HS, but that stat is really not that impressive. Mead High School probably had 100-150 boys turn out every year back when I was running in the mid to late 90s. I ran with them in the summers (another school) and I think they probably had 50 that were sub 5, probably 20 that were sub 4:30, 10 that were sub 4:20, 5 that could go sub 4:10 and 2-4 that were in the 4:00 to 4:05 range. Deepest program in the history of high school running. I won't believe otherwise.
Perhaps there is a Mead grad out here (or Pat Tyson himself?!) that could comment/confirm with some actual stats?