Ok.
Let the cops deal with gun violence.
I will tell with the examples yoir teacher has given.
1. Bullying: Group activities will help to make friendships among students. Hence, it may stop bullying. Also, if there are more than one groups, then the group will support their members if they are bullied.
2. Stereotyping: Can't think for this one.
3. Safety: Their can be self defence club or something like this. They can be taught some basics of self defence or what to do at the time of fire or medical emergency.
4. Lack of involvement with the community: They can help the needed. There can be monthly visits to old age home etc.
5. Environmental problems: There can be an environmental club. They can be given the task to look after school garden or clean the trash. That way, they themselves will not spread garbage here and there, because they know that they have to clean their class at the end of the week or day.