I'm a hoarder, a grandmother, and a teacher
Is there an adult in your life you can talk to in person about this? A lot of hoarding behaviors come from executive function (decision making) issues and overly emotional attachment responses. Both of those are things that you can work on, but especially at your age it helps a lot to have an in person support who won't judge you. Maybe you have a good counselor at school you could talk to? I'm betting that this affects your organization and preparation for school as well.