Think your Christmas shopping list is long? Back-to-school lists are even longer. As the second-biggest shopping season of the year kicks into high gear, 52 million parents are being tasked with buying more and more items for their kids' school needs.
TeacherLists.com, a website that hosts more than 500,000 school supply lists, reported a 29 percent increase in the average number of items per list from last year—now at 18 items.
"It's climbing rapidly," said website founder Tim Sullivan. "It's so many items now. A lot of the pressure from school budgets is passing onto parents, and parents are picking up that bill."
It seems parents are already aware of the extra expense. A recent survey from the International Council of Shopping Centers and Goldman Sachs found that 50 percent of parents were already planning to spend more this year compared with last year. The average household has allocated $672 for back-to-school shopping this year.
What could come as a shock to parents is what the schools are requesting on their supply lists.
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"The base is still the same," Sullivan said. "It's notebooks, pens and pencils. But what's growing the list is the extra items like hand sanitizer and Kleenex. These are items that no one's learning with, but the classrooms need those items."
Because parents are buying more items like paper towels, cleansing wipes and tissues, that could bode well for the retailers this summer, Sullivan said.
"If you're buying pencils, pens and notebooks, you're also buying backpacks, iPads and everything else you need like jeans and shirts," he said.
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The biggest gainers could be brick-and-mortar stores like Wal-Mart and Target. The ICSC/Goldman Sachs consumer survey discovered that physical stores would comprise 90 percent of back-to-school sales this year.
—By CNBC's Marqui Mapp