Lemome 2019-2020 Academic Planner for $13.56 at Amazon
If you only pick one thing on this list to help your child get organized, pick a planner. I know it's easy enough to keep track of everything electronically, but having a physical planner can be an effective way to get organized and keep track of everything in one place — assignments, homework, tests, meetings, clubs, sports, jobs, and whatever else students need to juggle. Another con of trying to do it all electronically is that many schools ban phones during classes. If a teacher assigns homework during class, students can easily forget about it before they have a chance to put it in their phones.
My high school issued every student a planner, so the habit of using a paper planner was ingrained in me, and I still use one today to organize my life. When a student has a physical planner with them every day at school, it will remind them to use it and keep track of their life.