Being involved in activities definitely reduces time for schoolwork, but it doesn't mean that schoolwork can't get done. Students can learn to manage their time, but they need to be shown how. There are many of us who, as adults, may not manage our time very well. And if a parent is not great at managing time, how will he or she teach their children to manage theirs? Even when adults are good at managing time, they don't always think to teach their children how to do what they do.
Because their parents might not talk about time management, I've spent many years teaching students (5th and 6th graders) how to find their available work time. I make these planner-type pages and have students fill in a sample week, so they can see where their available time is. When they fill in the practices, games, lessons, sibling practices, etc, they can then see what time is left in the day. If homework is assigned Monday and brother has practice, the student can see that they have a chunk of time from 3:30-6:00 (when they probably also eat dinner) and then 8-9:00. If homework completion can fit in those time slots, great! They can plan to use that time wisely. If it's not enough time, then they need to use another strategy to get things done. One of the fun parts of using the calendar/planner is the color-coding! When I used this for my own planning, I color-coded according to person (my son was green, oldest daughter orange, youngest purple, and I was blue:-).
If their chunks of time aren't big enough, students need to find other ways to complete their work. One of the strategies I share with students is to take backpacks and homework supplies in the car with them. When one of my three children had practice (they're all beyond this point now), the others brought any work they had to do. Sometimes homework was completed sitting on a blanket in the grass or sitting in the bleachers. Sometimes it was completed in the car while we waited. Do distractions occur when homework is done this way? Yes, they sometimes do. But, to me, using that time to work was better than losing an hour or two (or more, depending on travel time!) and then having to do everything after we got home (especially if we still had to have dinner!)
I also suggest that students try to study while they're driving to an event. They can read over notes and quiz themselves. If there are several people in the car, one person can quiz another. The student can quiz their parent as well, or explain information to mom or dad....this is a great way for a student to be sure his knowledge is solid.
I always suggest that students put upcoming tests on their calendars and then work backwards to schedule their study time....so they could label the driving time as study time. Projects should go on the calendar too, so students can again work backwards to fit in the necessary time to complete them.
The great thing about a week at a glance like this is that students don't have to depend on someone buying them a planner or printing out pages for them. They can write out their own schedule on their own paper and design it any way they'd like. Then they can post in it their room, on the frig, or keep it in a school binder.
As I mentioned, in the early days, I didn't quite know how to respond to students who didn't have time to do their work. But now, this is something I teach every year, to help avoid those "I didn't have time because...." statements :-)