Funny, I remember my high school and college coaches telling us to get our shoulders into the body. No one was ever taught to be a headhunter or go for the knees.
I presume you're talking about the same "high school and college coaching" that has resulted in this
widespread danger of concussion the NFL is currently addressing?
Steve Young and Troy Aikman were in high school in the '70s, Junior Seau and Zach Thomas were in high school in the '80s, Jay Cutler and Clinton Portis were in high school in the '90s, etc. It's not like players
just started headhunting; the only thing that has changed is the awareness of the symptoms, instead of just saying "oh, guess he got his bell rung" and the like.