VERY interesting topic, I have some questions:
1. You can expect a growing HS kid to gain a bit on velocity just due to natural growth. Does the spin rate change as well with growth?
2. 2200-2300 is not good according to PG, does that apply to a breaking ball as well as a fastball?
3. How do you get trackman to tell you WHEN it recorded the spin rate data?
1. It's unclear. Spin rate remains fairly consistent, as far as I can tell, after puberty. There have been some tests trying to determine factors on spin rate and it's still a mystery. For example, tests designed to measure the effect of grip strength on spin rate have found no correlation.
2. A majority of fastballs will fall in this range. From my minimal research, I'd guess that somewhere upwards of 90% of four seam fastballs will fall between 2100-2300 rpm. What this mean is that the majority of fastballs hitters see are in this range. The hitters mind must make micro-computed projections on the path of an incoming fastball. Given past experience, the hitter's mind will default to the path of a fastball thrown with this spin rate. Fastballs with spin rates significantly higher than this range will fight of the effects of gravity to a greater degree and follow a path that doesn't drop as quickly. Thus a hitter will often swing under a fastball with a 2500 rpm spin, because his mind computed it reaching the plate at a lower position than it in fact arrived. Alternately, a fastball spinning at 1900 rpm is more effected by gravity than the those in the 2100-2300 range and fall to a position below where the mind decided it was going to be. So, generally, if you could choose, you'd like to throw at a rate either a couple hundred rpm below or above the "normal" range. If you break it down, I believe you'll see much higher rates of swing-and-miss at the higher and lower ranges, given similar velocity.
3. On Trackman, if you attach your player to your account, it will show a graph with all of the pitches. Unfortunately, it seems individual pitch data only seems to be available for balls that made contact with a bat - fair or foul. When you put your cursor on the pitch, you get no information on other pitches, but on the ones included, you get date, opponent, batter's name, exit velocity, pitch type and result.
The numbers I used above came not from Trackman, but from the MLB PDP results and were recorded by a Rapsodo system. Through Trackman, I don't see any real vertical/horizontal break data.