Tom always described CV pace as "most bang for your buck" as far as stamina development went. I think for high school athletes, and probably even lower mileage college athletes, this is true. I think his training is fantastic for high schoolers with the mixed paces in most workouts and the focus on very easy recovery runs. The threshold and especially double threshold work is great for people doing enough overall volume but if you just run threshold workouts on 40-50 miles a week, I don't think that's going to be optimal for those types of runners.