You must be considered to be a full time student in order to be claimed as a Qualifying Child by your parents if you are at least 19 years old and have income of more than $4050.
See this
link for the IRS definition of full time student. A full-time student is a student who is enrolled for the number of hours or courses the school considers to be full-time attendance. So it's the school itself that decides who is full time.
I certainly would discuss this with your parents so that there is no confusion about this.