Is your son utilizing the resources available to him? Its been a long time but I was once a college athlete (late 80s - track). Our school has academic advisors specifically for athletes. This is pretty common in most schools. We were required to meet with them for our first year. After that it was left up to the athlete (unless they were failing classes) to decide if they wanted to continue on with regular meetings. The advisors were great with helping us figure out class load around our athletic schedule. Most schools have athletic - academic advisors.
I know I would normally carry about 18 to 20 credits during the fall semester as we did not start competing until the spring semester. This allowed me to drop my class load down to 12 credits during the season. Which I believe is the NCAA in season minimum. During the fall semester I would often have classes 5 days a week and at night as well. It sucks when others are able to setup their schedules to ensure they don't have Friday classes, classes before 10am or after 3pm but its one of the sacrifices you need to make when your an athlete.
In addition my advisor would work with me to figure out which were the easier/less "homework" classes and professors so I could heavily weigh my schedule with those classes during the spring semester. I know track is a little different animal and there is more down time, but it was not unusual for kids to study on the bus, at the field, or in the hotel room. Yes it was fun to be in a new city and head out before curfew to check out the area but many kids would stay back at the hotel to study.
From a social life perspective, it can be difficult as well. For an athlete it needs to be the lowest of your priorities. This can be difficult on kids as part of the college experience is the social life. During the season there is very little room for a social life. Again another sacrifice that is made by many of the athletes. We pretty much hung out either after returning from a Saturday meet at 1 or 2 in the morning or on Sunday afternoon. And then your friends are your teammates as they are the only other ones on your schedule.
Finally folks with kids heading into college to play a sport need to realize and prepare the child for the fact they now are "working" two full time jobs. Classes for 12 to 16 hours a week, homework for those classes will eat up another 12 to 16 hours, making it a full time job. Practices of 3 hours a day, plus weight room and training room for rehab equals about 20 hours of work a week. Once games start you are gone on the weekends from the school for about 10 to 15 hours at a minimum. It can be overwhelming your frosh year but you do get used to it as you progress through your college career.