Like other posters have mentioned a lot depends on the program, however very very few D1 programs, other than Stanford and the Ivy’s give their players the leeway to miss practice because of labs and other demands that science and engineering students have. I went through this with my son, who is an engineering student. When we were getting down to the final choices I started asking the head coach directly, “so coach, what happens when you have a practice that starts at 2PM and my son has a lab from 2-4PM on Tuesday and Thursday of the week - what are you going to say to him, how do you handle it with other players, and how would this impact his playing time?” One coach started hymning and hawing about it and, and Coach Stotz at Stanford came straight out and said we have kids coming and going all of the time, it is part of how we run the program. So to find out for sure you need to look at the rosters and see what majors they have, very specifically ask the coach. This is the one area that I personally got involved in the recruiting process since it is difficult for kids to pin down a coach on difficult questions like these.
My personal opinion is that science, pre-med, engineering and other lab dependent majors are not compatible with playing D1 baseball unless it is part of the programs culture. This means the coach is openly supportive, you go watch some practices and see it for yourself, and you confirm it with others on the roster. In the end it WILL impact your sons playing time, even if the program is supportive IMO.
Because of all of this my son decided to play D3 ball. His program is one of the top D3 programs in the country, but the coach is openly supportive and has kids coming and going all of the time. Even with the coming and going however his coach expects him to get his work in on his time. This makes it very challenging and it takes a lot of discipline to get in academic and athletic work in.
I will also be careful about thinking you can take Chemistry at JC’s during the summer as many schools will not allow it. I know my son’s school will not accept Chemistry taken at a JC because it does not meet their academic requirements.
Best of luck to you and your son.