Vivian Killebrew, left, and her daughter, Rae, 11, organize their purchases from sidewalk sales and garage sales at their Evanston, Ill., home. They also searched resale shops to get the most for their money.

MCT / David Trotman-Wilkins

CHICAGO — Vivian Killebrew set this rule for back-to-school shopping with her three children: If you want to buy new clothes, you need to sell some of your old ones.

The Evanston, Ill., mom hosted a yard sale last month at which her kids peddled the jeans they outgrew, the books they already read or the dress they’d long since forgotten. Brandon, 17, Ashley, 16, and Rae, 11, pocketed their share of the profits — the sale fetched $600 — toward their back-to-school budgets. The tradition reinforces two principles Killebrew works hard to instill: recycle what you no longer need, and money is best saved, not squandered.

“You’ve got to raise kids to stretch a dollar,” Killebrew said.

Many parents are capitalizing on this back-to-school season to give their children a crash course in financial literacy.

“Young people need to realize things can get tight in an instant and they may have to change how they think of things,” said Susan Taylor, who teaches family money management through the University of Illinois extension office. “As a family, they’ll be stronger for it.”

The reckoning comes as food and fuel costs cut deeper into household budgets, leaving less to invest in the annual round of doctor visits, registration fees, school supplies and clothes. Two of every 10 parents nationwide squirreled away part of their federal tax rebate check to cover back-to-school expenses — estimated to be $594 for the average family, $612 in the Northwest, the National Retail Federation reports.

“Parents may put off getting a new TV, but they want to make sure their kids are ready for the first day of school,” said federation spokeswoman Ellen Davis.

Pushing three shopping carts between them, Dena Walters and her four daughters combed through school supplies last week at a Target store. Walters said the family shopped earlier this year to avoid the last-minute frenzy. Still, outfitting kids for second, fourth, sixth and eighth grades is not cheap, no matter when or where you shop.

“I do it so they will be excited for school. So I called my husband and said, ‘I’m going to do it. I’m just going to bite the bullet today,’ ” Walters said. “But honestly, I have such a migraine right now.”

Melissa Tosetti, editor of Budget Savvy magazine, said the key to keeping to a budget is focusing on things that really matter to you. And for many kids, clothes matter.

“If clothes are important to a teenager, which they tend to be, work with them to figure out how to make the money stretch a little further,” Tosetti said.

The first question to ponder is: How much do they really need? Experts say there’s no simple measure of need. Factors to take into consideration include a child’s age, rate of growth, hobbies or even how often the family does laundry.

Next, before stepping foot in a store, families should take stock of what they have at home, Tosetti said. Then, it’s time to comparison shop.

Some parents say they encourage their children to stretch the budget and help the environment by mixing used pieces with new items.

Mara Lazar suggested her 12-year-old daughter host a summer clothes swap with her friends. Emma nixed the idea. But the pair searched through resale shops and vintage markets to find distinct, reasonably priced clothes for school. The practice comes down to priorities, Lazar said.

“I don’t think it’s a matter of doing better or worse financially. It’s a mind set: Let’s send you to summer camp and not worry about getting your clothes at Saks Fifth Avenue,” Lazar said.