**LONG RESPONSE INCOMING**
I don't think it's "select" baseball in and of itself. It's just the fact that these days that's where the competition is and in most cases you're going to get better coaching there. And that's how kids get better- playing against better competition and getting better quality instruction.
When I was playing Little League in Bryan North in the late-80's/early-90's there was no such thing as "select" baseball. In fact, there was only Little League. Nothing associated with PONY League or any of the other affiliated governing bodies like USSSA or Perfect Game or Five Tool/Nations. I know there are other national governing bodies that have been around a long, long time (like at least 50-60 years, maybe more) but in BCS back then it was only Little League.
You could play t-ball from like 5-7, minors were for 7-9, and majors were 10-12. Around the time I was 12 or so they created a "senior minors" division for 9-10 year olds (IIRC) to create some distance between the age groups and to put 10-year old kids who maybe just started playing or just weren't any good. I think tryouts for majors were probably in late-February or early March. Then we played a 16 game schedule over about 8 weeks. Then the coaches from the respective teams in the league voted on the All Star team. All Stars was the path to the state championship and regionals and eventually the Little League World Series in Williamsport, Pennsylvania.
The next year we had to jump from Little League rules and fields (46' mound, 60' bases, ~200' fences, closed bases, no leads, 2-1/4" bats) to "Junior League" which was under the aegis of Little League Baseball but went to "real" baseball. 60'6" mound, 90' bases, and generally 300'+ fences plus lead-offs, open bases, and big-boy bats. This was solely for the 13-year old age group and went up through the same All Stars to a World Series of its own. Let me tell you that was a tough transition- I mostly played catcher & 3rd base but played 1st and OF some and let me tell you those throws down to second or across the diamond from 3rd were LOOOOOOOONG. I don't recall anybody hitting any bombs over the fence at that point but trying to cover that big outfield made for a lot of triples and inside-the-park home runs.
Then for 14-15 year olds we went to "Senior League" which was again under the Little League Baseball purview and again with "real" baseball rules. Obviously the growth and maturity which comes from age made for better quality baseball and we started hitting bombs again and actually throwing out guys trying to steal bases. Again, there were All Stars which went up to an age group World Series.
There was overlap for most of us our freshman year of HS and our 15-year old seasons in "Senior League" but after that it was just HS ball. For years there was nothing but American Legion ball in BCS after the HS season ended and you had to be a stud to make the Legion squad because not only were the guys generally HS upperclassmen but the Legion team drew kids from more than just BCS but a number of surrounding towns.
Then the summer after my sophomore year in HS they started a Connie Mack league. I seem to recall the Legion winding down for some reason. In fact, the current American Legion Baseball website doesn't show a single Legion team in Texas anymore. Connie Mack is part of the AABC (American Amateur Baseball Congress) for kids from like 14-19.
There was no fall baseball or anything like that. Nobody did private lessons. No special facilities either. I didn't play with anybody who made the majors but I can think of probably a dozen guys who played either big time college ball (D1 specifically- whether a mid-major conference or major) and/or in the minor leagues for a stretch. I was also fortunate to have some really good coaches - a bunch of guys who played college or minor league ball and even a couple former MLB players. But that was really the luck of the draw. And it's night & day when looking at the overall skill level when I see a lot of good select players today vs. 99% of the guys I grew up with. Even most of the guys who played in college or professionally weren't as fundamentally advanced at such a young age.
I was a mediocre HS baseball player. The highlight of my baseball career was probably striking out on 3 pitches vs. Kerry Wood in HS summer ball (dude was like 6'5" 225# throwing 95mph gas at 17). Either that or hitting a 400'+ bomb off a friend who played at San Jac and in the Yankees organization for a couple years. Anyway, as a D1 football player I was a better athlete than baseball player. Maybe if I'd had the higher level of competition and instruction from a young age I could have been a college baseball player, who knows? Or maybe I wouldn't have worked so hard for football and developed there?
I used to be very opposed to our boys moving to select until about 11 or 12 but I got my mind changed 4 years ago when our oldest was in 7U league ball. There's a whole multitude of reasons but it boiled down to the fact that he just wasn't going to get the reps against competition to make him better. Same goes for our youngest- he turned 7 back in August and played 8U league ball in the fall and was by far the best player on his team. There were kids who were bigger and stronger who could throw harder and hit the ball harder but from a consistent, fundamental baseball perspective the years of him watching & playing with his older brother were huge but he's on a 7U select team now and he's nowhere close to being top of the roster.
I've said it before but it bears repeating- regardless of the sport they're playing I'm not really concerned with wins & losses at this point and nor am I concerned about having the best 11-year old or 7-year old (not even the best 13-14 year old either). I want them to win enough to keep it fun so they learn to love the game and see the success that comes with their hard work while competing against the best competition they can and keep putting in that hard work so that when they're 16-17 and close to full grown (at least in height) all their hard work at the fundamentals intersects with their athleticism and, in all likelihood, being 6'4"-6'5" for my oldest and 6'3"-6'4" for my youngest.
My 7-year old almost daily asks me to hit him grounders & pop flies and set up the net so he can hit off the tee or do soft toss. And even a broken wrist my 11-year old is insisting to go to practice so he can run, throw, learn the advanced baseball IQ stuff his coaches are teaching, and get all the cuts he can with his 1-hand bat.
My job as a dad with them is to love, support, and encourage them while keeping them grounded. It's different for the different ages but athletically I want them to learn to control what they can control; attitude, effort, and intensity. And be good teammates. If they put in the work the and give their best at those things they can control everything will work out.
Also, even with the low odds of advancing beyond HS in any sport, I find all the naysaying and hand-wringing over youth sports in America in general to be pretty ridiculous. Go look at what they do abroad in soccer- in all of Europe, the UK, and South America they take kids as young as 9-10 years old and put them in academies where they're away from their families and basically go to a boarding school where all they do is play soccer and go to class. There's a lot of this for baseball too in places like the Dominican Republic and formerly in Venezuela. Same for hockey in Canada and in the European Nordic countries- in Canada they take kids who are barely in HS and do the boarding school thing. In fact, one of the kids on my oldest's team is originally from Canada and has 2 older brothers who played junior hockey where at 14 they went off to boarding schools.
@baseballaficionado - let's pump the brakes on the Elite RBI team. Don't get me wrong, they're an outstanding 11U ball club, my older son's team played them a couple times in 10U. They lost both times but they were close games. Anyway, per their page on
Perfect Game they played up from 11U and beat one 12U major team.