MdngtRain and Jacq10 are both right. My boyfriend's mom actually called my school's counselor and told her that I was cutting. The counselor called me in the next day and wanted to have a chat with me. She said that as long as I wouldn't do it again, she wouldn't tell my parents. Since I was 15 at the time, I think she was supposed to.
Currently, I'm 18. I opened up to my t about my relapse when I was 17. She asked a few questions to get a feel for my reasoning of cutting and to figure out how much control I had. She knows that I have a lot of control and knows I'm safe about it, so if I tell her about any new cuts, she just tries to figure out why I did and and we try to work through that topic.
I would also suggest that you do ask the counselor what they are required to say. Usually, as long as you aren't suicidal and you explain that cutting is a form of coping with stress or something (if that is your reasoning for doing it) then he/she usually wont say anything to anyone. Since you are 19, I don't think that it will be a problem for you.
Please get help if you need it