Am I considered a full time student if I am in a co-op rotation?

I took a school approved co-op Spring 2016 and Fall 2016 and took classes on campus Summer 2016. While I didn't take classes during the spring and fall, I was still considered a student with it listing my co-op as a 12 hour (full time) course. I filed as a part time student because I only took classes during the summer but now I believe this to be a mistake. Is this the case, and can I change this if I have already filed?