you might not have the technical skills traditionally associated with art e.g. beautiful realist painter, awesome charcoal drawing skills etc. but there's still so many ways you can convey your concept...
like pezdog said you can try digital work or photography (where you can pick up the technical skills as you go especially if you art teacher or anyone else knows photography stuff)... you could do experimental work with paint, ink/ other art materials like abstract forms, patterns(where if you cant make things look real its to your advantage
), use found objects instead as sculpture materials (so even if yo usuck at ceramics, woodcarving etc. you can still do it), do a conceptual artwork like joseph beuys, christo etc. i remember some art express work was little bits of postage stamp sized paper which had notes written on it about daily stuff from that persons life... and it was still awesome in how they set it out and the concept behind it even if there didnt seem to be much technical (or what youd traditionally associate technical art skills with) skill involved. they mark on two aspects, conceptual strength and resolution...you sound like youll be fine with conceptual, but with resolution:
a) youve got three whole terms to practice and work on it
b) they're looking for you to do something well in that medium but also innovative use of that medium.. (if that makes sense ><)
i dunno , i guess with my huge block of text im trying to tell you that there's so ma ny possibilities you can do with your work that moves beyond what youd traditionally consider 'good' art... you're probably alot more skilled than you think you are so dont be so down on yourself ^^