Upload & Sell: On
While it will take a bit of hassle, I believe this is what is called a "teachable moment" by educators. I would actually make sure the school and if necessary district were involved because as all have pointed out, this is an illegal act. While I acknowledge the whole concept of "intellectual property" is morphing faster than I can keep up with, a journalism teacher/year book advisor absolutely should be maintaining the highest standards in a school publication. Maybe she didn't know. Possible, but doubtful. Lifting your work from a website would require public students, using computers paid for with public dollars, on school time to act illegally. This really is an issue that should be addressed.
I also work/shoot in a very rural poor area for the local paper. I was approached by the Superintendent's secretary - with whom I have an excellent relationship - about the year book using some of my images. I had only two requirements: (1) that ownership be acknowledged and (2) that they had to pay something for their use. It was a token payment ($40 for a CD with ~100 JPEG images). The advisor was adamant that respect for IP was a key part of what she was teaching. I wasn't trying to make money and certainly wanted to help out, but felt these principles were needed. I got my official $40 check and when the yearbook came out, my work was properly acknowledged. (Obviously, this was not a money making venture but an attempt to support the local schools. It was also obvious that the athletic pix were of a completely different quality than other photos.)
You might consider being proactive, approach the administration with your concerns, and offer to help students understand IP and provide "legal" pix at a very reasonable rate. Dennis' suggestion above is also a wonderful idea. This is an opportunity for kids to learn directly from the professional who did the work. In general I find high school kids more interested in talking to the "real world" than their teachers. (That hasn't changed as I was much the same way back in school.