Holdbacks are just legalized and organized cheating. Soccer is calendar year. that is how it should be for lacrosse.
Holding back a kid at this age or later is criminal (but if you are a top player, there's no holding you back in 6th/7th grade unless parents are lunatics). If a kid wasn't ready for K or 1st at the time that is a totally different story.
Happens all the time at 8th grade, MIAA has several top players that were just for lacrosse, Many are smart and do a prefirst in MIAA even if kid doesnt need it, MIAA parents know the drill, your boy will be at a disadvantage without being held back , most of reclass are joining MIAA late or made a mistake without prefirst.
No ,matter, you can hold him back in kindergarten ( prefirst) or any grade, no one cares,,,,but that shouldnt give you a right to play against younger players prior to high school.. there you can get your advantage