If you find yourself lugging lots of supplies from classroom to classroom, and maybe even having to make two trips, you may want to invest in a rolling tote. As you would expect, these bags or crates are equipped with all the compartments and pouches you need for books, pens, paper, and all the various supplies you need for your classes. If the bag is equipped with a telescoping handle, all the better, since it can take up less space in your car trunk.
Two good examples – the one on the right looks sturdier to me, though:
Teacher bags with wheels pictured:
Left: A+ Carry All Organizational Caddy by Learning Educational Products
Right: Educational Insights Teacher Tote-All Store-More Apron
Some of these rolling totes are made of fabric, while others are more like plastic crates. The plastic kind is more sturdy, but usually more expensive. You may want to choose the plastic crate kind if you will be packing things that can get crushed, such as rolled-up paper or anything fragile, like student art projects. Otherwise, a soft fabric type can be used. It has the advantage of being lighter, and possibly of folding up flatter. When dealing with this type of product, the failure points tend to be the handle and the wheels, so make sure these are sturdy and well attached.