This may be of interest...
https://www.cnn.com/2017/07/25...ins-study/index.html
Yes, for this particular test, the HS numbers are definitely less but still significant. The college numbers go through the roof. HS sample size was quite small. Here's another issue... let's say your kid is good. That means he'll likely want to play at the next level. Are you going to watch him have a great HS career and then when the recruiters come a knocking, tell him he can't play any more?
Also, as I said before, HS varsity is often very athletic man-sized individuals hitting very hard. Are the risks really THAT much different than college where the likelihood is overwhelmingly high?
As far as the teen drivers dying, that is definitely an issue. But there is not a 90+ % likelihood they will die if they drive. More teen drivers DIE from driving that they do from CTE but more teen drivers don't suffer neurodegeneration and significant challenges with physical and mental health later in life because they drove as teens. More teen drivers die from driving also because far more teens drive than play football at the HS varsity level or higher.