At all costs, teens don't want to look foolish in front of their friends. They won't ask for anything. They struggle with asking for things from friends so try to coordinate logistical matters in detail and in advance. Not for all children. But if so, be grateful this happens in junior high.
Some kids wait to go through it when they get to college.
They can go through weeks when they're just not focused or thinking straight. So, it they want to cut loose, this may not be a great time, but it is better to embrace the developmentally challenging years in junior high. I see people who are going through mid-life crisis in their forties. The destruction that comes from these crises because people did not have the time in their life to be rebellious can be major. If your teen's grades are waffling, it's better now than in high school.