If he's wanting to go on a mission...seminary will help a lot. As a missionary he's going to have to memorize scriptures and know how to teach certain stories from the scriptures. Seminary is an hour that will give him a heads up and a boost of knowledge before he hits the MTC.
I had to drive a half hour, one way, to get to seminary every morning. That meant waking up at 5:00 am so that I could be there on time. It was a real help to me in high school, getting me ready for the day and I stayed more focused in school because of it. Even though I was dead tired every morning, school went much more smoothly. I would push for him to go as much as he can. He will not only be blessed now, but in the future. Another way for him to think of it is, is he going to want his high schoolers going to seminary every morning? What is he going to tell them when they don't want to go? That he didn't go? Is that a good example? It is a hard thing to do every morning, I will admit, but in the long run, I am soooo greatful I got up and went.
