I mean, I think we all can agree* it would have made you a badass if you had done that. However, there's nothing* to be ashamed of for not taking action for fear of making your own life miserable, especially when you were barely in the double digit ages. Doubly so if you were also getting picked on to a lesser degree (like the airlines tell you, get your own mask on and make sure it is secure and you are safe before attempting to help others. You weren't a hero, sure, but this is not a blemish on your record.

I agree with the other commenter that the teachers should have been attempting to mitigate this to the extent that can reasonably be expected, and if they weren't then they should be ashamed (not you) because they were in a position of authority, not a peer. "Reasonably can be expected" because they might have been stretched too thin, not supported by administration enough, etc.