I understand. Been there and been through that. It's still a problem for me and I am now in my early 50s.
You need to establish a schedule, and stay off the PC until your home work is done, except for home work that needs use of the PC. And stay offline until the home work being done on the PC is done, again, unless it needs internet work. Once the work is done, then you can have some PC fun time.
I also like looking stuff up, too. I came across "fulgurite" today on a weather site, and looked that up. I won't tell you what it is because then I will spoil the fun you will have looking it up for yourself.
But it's nice to be able to immediately look up a new thing that we come across online.
I have news reader modules for news, politics, science, cooking, home repair and maintenance, car repair, humor, reference, and medical news. I also have bookmarks for many other types of sites. The medical sites help me with my health problems, and even saved my life several years ago. I had a health problem I wasn't taking seriously until I did some online research, so I got the help I needed in time.
Have fun with the PC, but don't neglect your school/home work. It will help you in your adult life. 
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If a man does not keep pace with his companions, perhaps it is because he hears a different drummer.
Let him step to the music which he hears, however measured, or far away.--Henry David Thoreau