This is one of my favorite tricks that I actually use all year long. Just not during school. We freeze peanut butter & jelly sandwiches. These are just like the store bought uncrustables, but better and much cheaper!
As simple as it sounds I will buy an extra loaf of bread or 2 when it is on sale. I let the kids help me and we get an assembly line down making the PB & Js. Depending on the size loaf you are going to get several sandwiches. I have even made them with gluten free bread. Put the sandwiches in ziploc bags.
I just line the finished sandwiches up right in my freezer door. For those days when you are running behind packing lunch, or running out the door, just grab a sandwich or two. They will thaw out by the time you eat them. In fact, my daughter prefers them slightly frozen now.
This is a great time/money saver for getting those lunches packed or on the table.