I don't know if bettas like blackworms, I get 10-15 pounds shipped in from California every few weeks. I use a pound or so weekly with my setup, and sell off the rest, getting more in when I get low. If I'm selling a full pound or more I sell it at my cost, smaller quantities I charge a little more, as I have to rinse them & change water every evening, as well as keep them refrigerated.
If you or someone you know is going back & forth from your school to the south side of Chicago let me know, they transport easily enough, though they do need fresh water daily.