My sons roomate had TJS. My understanding is that he was dominate in HS, with sliders and curves. Was TJS because of the slider and curve? Could be, could not be. He is used primarily in relief and as a closer only, one or two innings as he never learned to master some of the other pitches, yet.
My son is a sophmore, just learning to throw a true slider, which he will use as a show pitch only. Don't get me wrong, he did had a combo curve and slider he used as a senior, but rarely relied on it. If your son goes to college and has good mechanics, they most likely will teach the slider, but hopefully not to rely on. The curveball and slider is dangerous to young developing pitcher's arms, when used continually. If your son relies on his fastball and changeup and develops a decent breaking ball in HS, you have done the right thing. It's ok to teach the pitch later on, but not for a steady diet.
I may take some heat for this, but many overzealous parents and coaches want their players to dominate in HS, so they tend to turn their backs when sons use the slider and curve to get the job done.