Not impossible to parlay a public high school experience to the next level but really I've seen more kids show-up as pretty good players and by their junior and certainly their senior season they look like totally different players - reverse development.
What's more common, the HS player regressing in their development or the FS player aging out of Tier-III juniors without ever sniffing a "career" beyond HS? It's a rhetorical question.
Less than 60 kids at each birth year in MA will play beyond the HS or pay to play Junior level. Just keep that in mind as you and your player make your decisions. I have witnessed more than a couple of parents put hockey in front of not only school but actually use money they should be saving for college to "invest" in his development. It was a rude awakening for those families when their player aged out without much more than a sniff at mighty Finlandia U and he's suddenly a 21 year old freshman, no college savings and heading off to Bunker Hill CC because of poor grades.
That said, if you can afford to fund both, go for for it. FS will certainly lead to more development and exposure, just understand what you are really signing on for.
Not all kids WANT to go the Prep route and most local HS teams are just bad, so the best and only option is FS.
You could do the 1/2 season and then just deal with terrible HS hockey for a few months, but in most cases it's not worth risking an injury from a football player who owns a pair of skates and plays for his local school "for fun".
You know who rags on full season? The people who go to low in D2 and D3 high schools. Why? Because anybody with talent won’t even consider playing for their HS and the daddies get all upset when they leave and go 500 playing against seventh and eighth graders.
I have two boys. One that plays high school and one that plays club. Not even close in skill set and certainly not development over the last few years. The one that plays high school is not all that motivated with the sport so that’s OK. He even knows it. Sad part is he’s gotten worse. When the typical boy argument breaks out in my house we hear the words bender and duster quite a bit.
For each his own but please don’t kid yourself about high school hockey.