My son had trouble getting his 60 time below 7. He worked for months with a speed and agility guy, was lifting and doing other training, we read all kinds of advice, the number didn't budge. Summer after junior year, he started running every day, we videoed him, looked at every piece of his body we could think of, compared him to people running fast 60s on youtube, counted the number of strides, watched videos of famous sprinters, etc. After about 2 months, something happened - either his body changed, or some piece of technique clicked in his head, or both, and he dropped .3+ seconds. It didn't happen in the timeframe he wanted, but it did happen. He learned a lot about how to study technique and apply it. What I'm saying is, your son may be at a physical limit for now but at some point will make a jump, or he may need some other piece of mechanics in his brain.