I'll agree with pretty much everything that was said above. FYI, MKS, we are in California too. My guy was a 13 year old high school freshman and two years younger than his peers.
If we could do it over, we'd take one of two paths for that son: 1) a post graduate program at an academically oriented high school, e.g., a boarding, prep school; or 2) a gap year with some college classes, work to make $, volunteering, church as a family, etc.
Should the student be a rising Senior now, then in both cases above, the student-athlete would be a "Class of 2021" instead of 2020 if he takes the PG or gap route. College coaches simply need to know which year a student-athlete will be. It's not a negative to take a PG or gap year.
As others have noted above, there are fantastic high schools that offer a PG year. The baseball varies as it does at high schools everywhere. Everything else varies too: costs, weather, academics, # of boarding vs. day students, college counseling, etc. I am happy to share my thoughts on any school as we visited many...too many but that's another story.
Boarding schools can be expensive, so an alternate route is a gap year somewhere. Doing this gap year at home allows for courses at a local college (though not too many courses so that NCAA eligibility is affected), dinners at home, worship services as a family, a job to make money, volunteering, training for baseball or other sports, etc.
Our experience at IMG was negative. I've posted a number of times about this. My son played D1 baseball, but he didn't need to go to IMG to do that. The paths above would've worked just fine IMHO.