Not only has back-to-school shopping season already started, it’s been underway for several weeks for many shoppers. According to a National Retail Federation survey, 23 percent of consumers with children in grades K-12 said they began shopping for school supplies at least two months before school starts as a way of saving money.

But teachers say saving money by skipping some of the items on school supply lists is not a good idea. “I go down to the bare minimum,” says Elise Kreitner, a fourth-grade teacher in Johns Creek, Ga. “We have been really aware” of the expense.

Kreitner said that binders and folders — tools for keeping papers organized — fall on and off the list of required supplies at her school. This may be something you can individualize and save money on, as long as you provide a system for organization.

Here are more tips to help you save on school supplies:

Harness the power of group buying. Jennifer Kraften, a gifted and talented teacher in Atlanta, said some families pool funds to purchase items like glue sticks and wipes in bulk from office supply stores. Using coupons or loyalty cards at those stores can help you save even more.

Buy in advance. One year in advance, that is. Kreitner shops whenever back-to-school items go on clearance. She takes her husband and her brother-in-law along to help her get as much as they can carry. “I am a hoarder of that stuff because I know I am going to need it for my kids or my students,” said Kreitner, also a parent of four.

Communicate with the teacher/school. Teachers say they will always work with parents to make sure a child has necessary supplies. Ask the teacher if there are some items you can wait to buy. Also, ask if your school might consider participating in programs where you buy a prepackaged set of supplies at a discount through a third-party vendor and get free delivery to the school.

Shop at home. Before you go to the store, round up forgotten items in your home that kids can use for the coming year. Arrange a swap with other parents. You may have a huge stash of pencils, while someone else may have scored a deal on paper. Trade what you can and buy the rest.

Watch the ads. This time of year, most office supply, department and discount stores are running promotional specials.

Beware of backpacks. This is one of the largest expenses, and every child needs one. While you may automatically reach for the least expensive backpack you can find, pay attention to quality. Find the best quality backpack you can afford to make it through the year, if not a few years.