in 10u pitchers are just coming around to hitting spots consistently, while still being able to field their position properly, and maybe throw that change-up once in a while while not giving up walks. 12u you start seeing pitch locations start controlling the pace of the game, speed of pitch vary, and some braking balls. Should be able to know the situation of position for bunts and slaps, and develop knowledge of pitch when there's a runner at 1st, 2nd and third, bases loaded 2 outs, etc. 14u you start to appreciate breaking balls and change of speed pitches, while adjusting to the mound distance. 16u and 18u is a beauty if your pitcher has been trained right.
10u parents, remember, its a marathon, not a sprint. Appreciate your athletes as they progress through the hardest sport ever invented, and the position most demanding. I've seen too many stud pitchers get burned out by 16u when all they knew at 10-12-14u was how upset their parents & coaches got by messing up "that one time".