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 / Updated  / Source: NBC News

A majority of Americans believe college is an investment in their child's future, but it's one they're not adequately preparing for.

Only 48 percent of parents are saving for their child's education, down from 51 percent last year, according to Sallie Mae's new "How America Saves for College 2015" report, which surveyed 1,988 parents with children younger than age 18. Families' average college savings balance has decreased, too, dropping 25 percent from $13,408 in 2014 to $10,040 in 2015, the lowest level in three years.

That, despite 89 percent of parents telling Sallie Mae they expect their child to attend and benefit from college and 84 percent saying they're willing to stretch financially to make that college dream a reality.

It's not that Americans aren't prioritizing college savings, said Michael Gross, head of the higher education practice at market research firm Ipsos Public Affairs, which conducted the study in conjunction with Sallie Mae. While people tend to dedicate about 10 percent of their total savings for college, the overall pool of funds for saving toward goals, which included retirement and a new car, has dropped.

"It's a byproduct of there being less savings altogether," Gross said. "The truth of the matter is, when we ask people why they're not saving, they say, 'I just don't have the money right now.' "

Families who aren't saving still expect that, come tuition time, their savings and income will cover 29 percent of the bill, according to the study. (Savers expect to cover 41 percent.) That may prove a tough goal for procrastinators to hit. "[Even] if you start saving as soon as the child is born, you only have 17 or 18 years," said Joe Clemens, a certified financial planner and founding partner of Wisdom Wealth Strategies in Denver. Versus, say, the 40-plus stretch a new college grad has until retirement.

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-- Kelli B. Grant