"To become contributor you need to submit at least 14 pieces of art. Once you are moved to contributor you will be invited to be a Prefect. After you are promoted to Prefect and show great leadership you'll have a chance to become headboy or headgirl."
Thanks for asking the question I realized it tell you how to become contributor!
So to answer your question: Yes you can become one but not right away, sorry. And I will place you in Gryffindor~