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Budgeting for school? Check the 'Backpack Index'

Shoppers aren't planning to spend as aggressively on back-to-school items this year, but there's one area where they should expect to shell out additional cash.

Parents with children in elementary, middle and high school should budget an average of an additional 5 percent for the cost of supplies and extracurricular activities, according to Huntington Bank's annual Backpack Index. Huntington calculates the index by examining classroom-supply lists from schools in the six states it serves: Ohio, Michigan, Pennsylvania, Indiana, West Virginia and Kentucky.

Those with children in high school, in particular, will be hit harder than last year, with costs expected to jump 9 percent to $1,402. That compares with a 2.5 percent increase, and $941 in expected spending, for middle school children, and a 1 percent rise to $649 for elementary school parents.

For parents with one child in elementary, middle and high school, they can expect to pay as much as $3,000 on supplies and extracurricular activities, Huntington said.

"With the ongoing slow growth in wages, it is difficult for many families to meet the rising costs of sending children to school," said George Mokrzan, director of economics for Huntington Bank. "For a family of five living at the poverty level guideline of $28,410, the cost of sending three children to school would consume as much as 10 percent of their income."

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Huntington's Maureen Morrissey Brown said there are several reasons why costs have risen every year since 2007, when the bank first created the index. During the recession, for one, school districts either imposed or increased pay-to-play fees, while the price of musical instrument rentals also rose.

The list of required supplies has also grown over the years to include more costly calculators, thumb drives and flu-preventative products including hand sanitizer.

And among the high school set—the costliest of all K-12 students—kids are taking more college admission tests.

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As costs rise, a separate survey released by Deloitte earlier this week found that 39 percent of respondents plan to reuse some of last year's school items instead of buying new. That's up 13 percent from 2011.

Among households with an income of less than $100,000, the proportion of people who plan to reuse last year's items rises to 45 percent. By comparison, only 31 percent of households with $100,000 or more will do the same.