Only 33% of parents are investing in college savings 529 plans, and only 20% of households earning $150,000 or more are taking advantage of them, according to a Gallup survey commissioned by Sallie Mae.

“I’m surprised at how many people think everyone gets some financial aid,” financial planner Linda Leitz told Dow Jones. Of the wealthier families that are not using 529 plans, Leitz said she expects many of them are relying on the grandparents to pick up the college tab. But given the average annual $50,000 price tag at private college, Leitz said, parents may be overly optimistic about their parents’ generosity.

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