I would imagine there are already many differences in culture between different types of schools, and in different places--English school cultures is going to be terribly different from American school culture. I'd say your first step would be to decide where (and
when!) your fictional school is placed. Then you might ask people in your acquaintance about their experiences, if they've been to a similar school or had similar experiences. I expect it'll be different for boys and girls, too. And different depending on their own family's affluence or community standing or any number of smaller details that affect the way people interact.
You could also read stories that deal with such settings as you're looking to write. You could find Youtube videos from people who are actually students at a high school, and who talk about their experiences. There's probably an awful lot of data about things like high schools, which is an experience so many people have gone through. It seems like the stereotypes have been somewhat engraved in American culture now, although that may or may not be helpful (stereotypes rarely are).
(Granted, you probably want to take everything I say with a grain of salt, since I was homeschooled and never experienced anything like a high school. On the other hand, maybe that makes me a good person to ask, because that means I don't know much about the setting myself and that's how I think
I'd start trying to figure out how to write about a high school setting.)
Also...maybe talk to some high school students, if you know any? If you don't, maybe come up with a good excuse to go and meet some (giving out free oreos? I don't know) and ask them what it's like. There are so many children in a school, there are bound to be plenty who are happy and excited to help you out with providing an accurate setting for your book, if you tell them your questions. Some of them may even be interested in creative writing themselves, and in trading opinions and experiences with you.
(The belief inherent in my advice here, of course, is that teenagers are actually capable of being normal and rational human beings, a belief that honestly hasn't been very prevalent in modern times....
)