Deku might be completely shocked at first. Since Bakugou has always been so aggressive towards him, he would never expect such a confession. He might just stand there, mouth agape, not knowing what to say.
He might cry a lot. Deku is very emotional, and being cheated on would be a very painful experience for him. He could also get angry, which is rare for him, but this situation would be so unjust that he might not be able to hold it in. He'd probably start to question his self - worth too, thinking that there was something wrong with him that made his partner cheat.
Deku might be initially shocked. He's used to Bakugou's aggression, but an actual injury is different. He could be in pain and disbelief at first. Then, he might try to downplay it, especially if he doesn't want to cause trouble for Bakugou, because Deku is generally a very forgiving character.
Well, some might be really amazed. They could see a new side of Deku that they never knew before. His singing might show a different level of confidence or a hidden talent, so they would probably cheer him on.
Some characters might try to understand Deku's motives. Kirishima, who was close to Bakugou, would be angry at first but might also try to find out if there were any extenuating circumstances. However, many would be afraid of Deku, seeing him as a threat now that he has killed one of their own.
Some classmates might be understanding. They could have been taught to be inclusive and kind, so they don't make a big fuss. However, there are also likely to be some classmates who are curious or even a bit mean. They might tease the child, not fully understanding the situation.
Uraraka would be heartbroken. She was one of Deku's closest friends. She might lose some of her usual cheerfulness and become more focused on finding out who or what was responsible for his death. She could also struggle with her own self - confidence in using her quirk, as Deku was always an inspiration to her.
Well, in fanfiction, his classmates' reactions can vary widely. There are those who are his friends and they would be supportive. They might cover for him when he has to run off to be Spider - Man. On the other hand, there could be classmates who are envious. They might spread rumors about him or try to expose his secrets just out of spite or envy. And then there are the classmates who are just indifferent. They don't really care about Peter's secret life and just see him as an ordinary classmate most of the time.
His classmates would probably be very concerned. Some might immediately run to get the teacher or the school nurse. Others might gather around Peter, asking if he was okay and trying to comfort him.