Tbh I'm not as familiar with golf but my stance on high school sports was to focus on ONE sport and play it all year around. This most likely means a school team then when school team is done for the season, play the remainder of the year with club team to maintain/develop skills in the "off season"

^This is mainly if your kid plays competitively and/or training for college sports teams. 
 

If your kid is playing for fun in high school then they may want to keep some variety (play different sports) and they may not wish to play sports all year round 

From what you have said about your SS.. golf is not going to be for him... haha.  It's an incredibly frustrating game.  I have a relative who is on the PGA tour.. and it's the smallest of changes that can upend  your game... and most people who play will tell you it can be quite frustrating..  unless your SS has a natural talent for it.. (and even then).. he will probably not enjoy it.

i paly golf and it is an expensive game, especially for kids as they grow so need clubs regularly [every 6 to 18 months], that can be up to 2k. it may have been recommended to improve his swing in baseball. 

My daughter played in high school. It's been a while but I think the season is more spring time...at least here. We were responsible for her golf clubs, shirts, tournament fees, travel expenses, etc. She also had to have a membership at our local golf club. All of her practice times were during school. Tournaments were on weekends

My daughter did a lot of sports in school but it was always one at at time.Track, basketball, softball and golf. Nothing overlapped. 

Depends on size ect. You must but golf clubs the bag.  School should supply tge shirt. School colors ect. There must be a golf sport season. Since most high schools don't have golf clubs on there property. Kids must travel every day to practice.  
In general high school sports are big.  Most kids have private coaches for batting.  [ hitting and pitching are the two most important things]. A really good pitcher or hitter will get college scholarships.  So investing a few thousand in high school can save you $400,000 in college cost 

Seems to me he's on the old side to start competitive golf. I have a friend whose son was a competitive player (and became a national junior champion) and from what I understand,  you need to start REALLY young. Besides that, it's a very expensive sport to just goof around. Also, the season may be only a few short months but you absolutely have to train all year round to keep up your level and progress. It can be very intense.

I have no words.

Though for us it was not a huge time commitment. My Military School had a 9 hole course so we just walked about 10nins and played.  We played for free and anyone in town paid a green fee to play if they were not club members.

I was never particularly good. I would compete in tournaments with other schools if someone else was not available.  

As with anything, to be decent takes a ton of work, to be great, it takes a ton of work and talent.  

I find it interesting that a kid with two batting coaches who won't take advice from the professionals thinks he can play golf where swing mechanics are far more critical and far more complex than hitting a baseball. thinks he can play on a team.

Golf is likely going to be an extremely humbling experience for this kid and his coaches will hate him when he dismisses their guidance and coaching.  There is no pithcing to somewhat mitigate his lack of eye had coordination to hit a ball.  In golf, there is only hitting the ball.  There is no other action. No throwing, no running, etc..

Buckle up kid. This is gonna be a learning experience.

Okay, so has he played golf before? High school is super late to pick it up competitively.

My HS boyfriend played starting when he was like 3, played all through high school and college, and was on the PGA tour for a bit. So my perspective may be skewed because his experience wasn't super typical (though multiple PGA players came out of my HS in this time period), but it was a huge time and financial commitment. There were boys who played just because they liked it and it was a good way to get out of school for an entire day, several times a semester. Similar to track and field in that the tournaments were usually during the school day. He practiced every single day after school, year-round, and usually played for several hours on Saturday too.

As for the multiple sports thing, I participated in 5 varsity sports and it was a very good thing for me. It forced me to manage my time and be highly disciplined. If I had buckled down and focused on one (volleyball was my best one), I possibly could've played in college, but I never regretted doing everything. That being said, my parents were on the same page about it all. It was different in the late 90s, I don't think parents gave much thought to activities taking kids  away from quality family time. The mentality was more, keep them busy/out of trouble, and build a good resume for college and call it good.