If you aren't familiar with Shutterfly, you should definitely take a look at their site. At least once a year, often multiple times, you can find or are sent a code to receive a free photo book. All you have to do is pay the shipping ($8). They run lots of deals through Facebook, too, if you pay attention to them.
If you use this address (https://invite-shutterfly.com/x/tPgSMF), you can get 101 free prints, if you're a new customer.
Do you keep a memory book or something each year? I'd be interested to learn how other teachers store memories from each year.