While I am all for FREE, it is also important to think about safety. Be cautious when selecting storage containers. If you are using recycled cans, be sure that there are no sharp edges. Use your judgement when picking glass containers.
Also, check to see if your school has a policy on using them. Some don’t allow any glass items. If you are working with very young children you might not want to allow them to have access to Ziploc bags.
I love these glass jars, but would hate to think of them shattering.