This isn’t the slam dunk you seem to think it is. Of course *most* parents will do what they *think* is in *their child’s* best interests. Yet, the only issue worth considering is whether a rule or operating structure rewards what is or is not objectively in the best interests of the sport and - more importantly - the children, individually AND collectively. That's called policy. From a policy vantage, it’s suicide for a sport that must grow or stagnate (or die) to exclude participation at every level based on socioeconomic status, which is what the current set up does. If you are part of the 90-95% of parents without an extra 15-45k to throw at private school for an extra year and beyond, or your child is not gifted enough to get a full freight or even partial scholarship to private school in 7th/8th/9th grade, you’re excluded. That’s wildly self-defeating for the sport as it attempts to grow - which it desperately must.
Moreover, kids have been doing sport-driven post grad years (what this used to be called) for a long time. I actually did one at a New England prep school for football after graduating public school in the early 90’s and (1) it totally helped both my college search and subsequent college (and college athletic) experience and (2) it was pretty fun and perspective broadening. The difference is that really only those talented enough to warrant consideration for that at age 17 or 18 were considered, which is as it should be, as it is a transactional deal btwn the school - which keeps alumni donors happy with a winning program and perhaps gets some profile - and the athlete, who gets a free or partially subsidized prep school education and all the networking bennies that come with it. But again, that was high school, not middle school. Now, you are correct that it’s nearly condition precedent to be older than the norm IN MIDDLE SCHOOL if you want to play higher level college lacrosse, which as noted is socioeconomically exclusionary due to the public school age/grade requirements. It should be obvious that this is not good for growing the game, to put it mildly.
Finally, repeat K-8th grade and repeat it again all the live long day if you can, and if you believe it’s in your child’s best interests. I’m sure you’re correct that families that are able to do allow silly name calling to influence their child-rearing decisions, nor should they. The schools will not turn down the tuition and clubs will not turn down the fees and the college coaches will not turn down a more mature athlete, and again, why would they? But it should be obvious that that doesn’t mean they should also play in the same grade in K-8. They should play like-aged athletes for safety and for growing the game. Entirely severable concepts.
So argue all the above all you like. But “everyone who can does it” and “I’m acting in my kid’s best interests” arguments, which are true (mostly) are not even close to dispositive and simply highlight a system in dire need of overhaul if the sport wants to scale beyond a few major centers for a few affluent families. | 
