If I look at MYHR 08 rankings in 2019-2020, there are 4 Boston area teams in the top 20 (BJE, TopGun, Flames, Islanders). Looking at the 08's this year, there are still 4 teams (MSC, BJE, SPA and RiverRats Half). Are those teams all the same kids? Of the roughly 68 kids that played on those top teams in 2019, how many of them are still playing in the Boston area at a high level?

If EP is accurate, at least 8 of the kids on MSC are not from Boston but from FL, MN, CO, etc.. and at least 6 of the kids on SPA are foreign, so there has got to be some churn. If there is churn, where do the new kids come from?

No they are not the same teams/players. In our area, top teams are generally dominated by a few players that are actually elite, surrounded by good to really good players. As kids move out of youth hockey into their next phase, those few elite players get recruited to play with other elite players at places like MSC, SKS, SSM, ISL preps, etc. The pool they are drawing from is no longer the 30 minute drive from their home rink but limited only by the interest they can create.

I suppose I could take the time to try and look up the rosters and search each kid but I'll take a guess. Of the 68 or so players, probably 65 are still playing hockey, 20 or fewer are playing what I would consider "high level" hockey, the rest are playing a combination of full season, attending a lower level hockey academy or playing high school. Of those 45 or so kids, some will continue to develop and find their way back to higher levels, most will not.

I would say this is pretty accurate. The elite players will always have a million options, the vast majority will end up in sub par programs, not develop and play low level before hanging up the skates. Happens literally everywhere not just here in New England.

Definitely a fair assessment, think of how many players who currently play ACHA or low level D3 played with players who are now playing at high level NCAA and pro levels.

The elite players go on to continue to be elite, while the good players who are not bad but not elite per say, go on to try to make something of their hockey careers, the opportunities are more limited, but it is possible for a few of these good players to make it to a high level. The majority however will just stop playing all together, and then of those who don't continue to fill in the ACHA and lower D3.

If there are ~20 kids that are the same, do ALL of the "new" 48 kids come from different geographic areas or do some local kids who weren't as skilled at younger age improve when they are older and join the group?

The other players come from other geographies, area teams other than the four mentioned, etc. You don't seem to understand that there are elite players not playing on the top four "elite" teams in New England.

Yes, this is also part of it. A lot of kids play different places/things get watered down with high school/prep schools. As opposed to other areas where kids continue to play AAA

Nobody is truly elite until they make it to the NHL.

-BJE core is partly intact from 19-20 although they also pulled TG's best player when that group blew up in the off-season.
-TG was absolutely decimated. Kids left for BJE, Mount, BK, and Rats.
-Flames top kid went to Mount. Domino effect.
-Islanders were generally a bubble top-20. They lost kids to prep, pre-prep (Cardigan) and elsewhere. One even went to Windy City.

SPA got good last year, then added the foreign kids plus VT defenseman.

EC Militia was also an option for 14U this year. Not mentioned but BJT also had a decent squad 19-21. Iggy went to BC; another top kid at BK.

At 14U, a high-end talent can still be a point-per-game kid but depth and physical maturity start to carry more weight.

Interestingly, the biggest Fed drop-off from 19-20 was MFR (#1 then; #20 today). They started '22-23 only down 1 top kid (BK) but started slow and then lost another kid mid-season to Gulls. Even with minimal turnover, a team that dominated squirt and peewee is no longer a powerhouse. That's youth hockey.