The other characters would be very concerned. Dewey, the teacher, would probably immediately rush to her side and make sure she gets proper medical attention. Zack might be in shock at first, but then he would step up and try to take on some of Summer's responsibilities in the band, like leading the rehearsals. Freddy would be constantly checking on her, bringing her little gifts to cheer her up. And Tomika would be the one to comfort Summer emotionally, listening to her fears and frustrations about getting hurt and being unable to perform for a while.
If Summer gets hurt, the other characters would be deeply affected. The whole band would feel a sense of loss as Summer is an important part of their group. They would start to realize how much they rely on her energy and talent. Some might feel guilty if they think they could have prevented the accident. They would all do their best to fill the void she leaves. They would try to incorporate her ideas and suggestions even while she's recovering. And when she finally recovers, they would throw a huge welcome - back party for her with a special performance dedicated to her.
When Summer gets hurt, the rest of the group would react in different ways. The more practical ones like Lawrence would start making lists of what needs to be done to keep the band going in her absence. The more emotional characters like Katie might break down in tears at first. However, they would all come together as a team. They would visit Summer in the hospital or at home regularly. They might also organize a little concert just for her in her room to show their love and support. They would encourage her during her recovery and be excited for her return to the band.
Perhaps Summer gets hurt in a rehearsal accident. For example, some equipment malfunctions and she gets a minor injury. This could lead to a story where the kids in the School of Rock learn about safety measures in a more serious way. They might have to postpone their shows and face the disappointment of their fans. Meanwhile, Summer could be feeling frustrated and left out, but her friends visit her often and they come up with creative ways to keep her involved, like having her write new lyrics from her hospital bed.
Yuki would likely be very concerned. He has a soft spot for Tohru and would probably rush to her side, trying to find a way to help. He might even blame himself if he thinks he could have prevented it. Kyo, on the other hand, would initially be angry, but that's just his way of showing worry. He would be more hands - on in getting her the help she needs.
Beast Boy would definitely be one of the first to react. He and Raven have a special bond in the Teen Titans, so if Raven gets hurt, he would be extremely worried. He might use his shape - shifting abilities to quickly get to her side or try to find help.
Simon might be in a bit of a panic. Since he's her friend and also not as used to the dangerous situations as the other Shadowhunters. He'd try to do whatever he can to help, like getting help from more experienced Shadowhunters or trying to comfort Clary while she's in pain.
The other characters' reactions can vary. Pixal, if she's around, would use her technological knowledge to see if there are any internal damages to Jay, especially if it's related to his electrical components. The villagers of Ninjago might also show their support. They could bring food or offer shelter for Jay to recover. The reaction of the villains would depend on the situation. Some might see it as an opportunity to finish Jay off, while others might be impressed by his courage in getting hurt while fighting them.
Li Shang would probably be very concerned. He might blame himself for not protecting her better. He would immediately call for the best medical help available and stay by her side until she recovers.
Anakin, if he's in the story, would likely be very protective. He might rush to her side immediately, using his skills to try and heal her or at least stop the bleeding. His reaction could be full of anger towards the cause of her injury, vowing revenge.
It could be a rival music group. They might be jealous of the success of Summer's band and try to undermine them. For instance, they could spread false rumors about Summer which cause her emotional pain.
Another plot could be that Summer faces some kind of personal attack outside of the band that makes her question her place in the School of Rock world. For example, she might be bullied by other music students. The fanfiction could detail how she copes with this hurt, and how her friends in the band support her and help her regain her confidence.
If Jules has a family member in the Flashpoint story, they would have an extremely strong reaction. They would rush to her side in the hospital, if it comes to that. They might even try to convince her to leave the dangerous job. Their reaction could add an extra layer of drama to the fanfiction, as Jules would have to balance her family's concerns with her own dedication to her work.