10u, wristbands didn't exist much or at least in our lil world
11u-12u, lots of game decision teaching, body part signals, and we considered switching to the wrist bands.
13u-14u, time to "play" without us holding your hand. Tried the number system, some liked, some didn't (pitchers and catchers) so we didn't mandate across the board. So, they called most of their own plays at the plate and on the bases. 14u was also the year they called all of their own games. Defense also had "stealth" calls. Catcher has signs that most won't notice, what I call "ninja softball". So, for "me", it was about letting them "see", then "communicate", and this is from the plate. defense, offense, bases, etc. So why would I do that. Well, yeah, many times "learning in the trenches" is way better than my interpretted whomp whomp whomp waa waa (Charlie Brown's teacher) and got their softball IQ way up without them listening to my rambling for hours at practice and then having no interest in executing in the games. So my signs would 'occasionally' be called in just to mess with the other team and then the girls still had nearly a 100% "read and do" set of commands. There were calls that were "have to do's" out of tight game strategy but I'd communicate that during the inning or between innings. So, for me, the long term deal was to get their IQ's very high and then when they play for coaches that live by calling every play in... they would be very sound mentally and have the ability to make micro adjustments on the fly and understand the repercussions of their results and split-second decisions. The coolest thing is when they "know it's ok to bunt with 2 strikes and 2 outs" and make a play and "NEVER" get yelled at for it and have confidence in laying down the crucial bunt or play or whatever. And, BTW, many games are won due to the players playing it out this way, I love it! Takes a long time to develop this but it's the right thing to do for me and my style when I coached.