So noisy!

I'm a third-year high school student, and even though our homeroom teacher arranged for us not to be too loud after class and school so we could catch up on sleep or study, a bunch of people in the class are still being really noisy (ー`´ー) Even during non-major classes, they're constantly loud. They keep chatting while the teacher is talking, and after being told to be quiet, they start making noise again. Today was someone's birthday, and they suddenly started singing "Happy Birthday" at noon, deliberately really loudly. Even though many people in the class don't know him well, it felt like our whole class had to celebrate his birthday. After school, most people left, but a lot of our class stayed behind and were being loud. Can't a person study? It's so annoying.