Is work you create in college counted as yours or the colleges property? (Copyrights etc)

Hi guys, I attend an IT and have recently created a visual piece of work for an assignment. The lecturer of the module is friends with people who are currently putting on a festival and has decided that the work we create could fit with the theme of the festival (this is all in the brief) and that she could work with the festival organisers and use our work in the festival, I was ok with this idea as when it was put to us, it seemed as though our work would be displayed at the festival with no mention of financial gain for anyone which I was ok with. Now it has come to light that the festival people might be using the work to put on merchandise such as post cards, t shirts etc. I am not ok with this at all as this festival already has loads of grants and sponsors etc and it was never made clear to us that our work would be used on merchandise with no money getting back to the students. I'm just wondering does the college legally own my work which I create for assignments and can do with it what they want or can I have the final say on what is done with it? I haven't uploaded the file yet and if it turns out the college can do what they want with it I'd be tempted to put a watermark or something on it to make it somewhat unusable for merch.... anyway sorry for the rambling! Thanks for any help ye can give!