With almost any question, one can find exceptions to the answer There are 30 teams in MLB, each with a 25-man active roster, so you have given us the one in 750 example. 
Matt Tabor.
Again, there are 247 minor league baseball teams, so roughly 5000 players at any one time - 90% of whom will not make it to the big leagues.
High school baseball in New England can be not great but prep baseball is actually pretty good. Salisbury, Avon and Andover have been the powerhouse teams. Salisbury finished the 2014 season as the 8th ranked team in the country. The coach of that team went to Cheshire Academy and has quickly built up that program. My sons team is average at best and still has 4 or 5 guys that should play baseball in college barring injury. Andover probably has 10 or 12 players of that caliber.
You could look a little bit further south. I think the Mid-Atlantic Prep League teams have a decent season.
I will preface by saying that I know almost nothing about baseball. But one thing I’ve noticed about baseball at Andover is that it seems to get a lot of love on the school’s social media.
I imagine that if a school is able to field a varsity, JV, thirds or more teams, there is a greater likelihood that that sport is the primary sport for many, if not most of the varsity members (with crew probably being the exception given there are so few students coming in with prior experience in the sport). This topic seems like a good one for your child to ask about when contacting coaches at prospective schools.