WASHINGTON — A little-noticed provision in President Trump’s sprawling new tax law is treating middle- and low-income college students as if they are trust-fund babies, taxing sizable financial aid packages at a rate first established 33 years ago to prevent wealthy parents from funneling money to their children to lower their tax burdens.

Higher-education leaders are calling on Congress to fix the provision, which drastically raised the tax rate on so-called unearned income for children with assets and young adults in school. Students with large financial aid packages are finding their nontuition assistance for items such as room and board taxed by as much as 37 percent, even if their family income tax rates are much lower.

The impact on full-time undergraduate and graduate students under the age of 24 went largely unnoticed until the waning weeks of tax season. But word is spreading. About 1.3 million undergraduate students and 15,000 graduate students have scholarships and grant aid that cover nontuition expenses.

Ted Mitchell, the president of the American Council on Education, a Washington trade group representing 1,700 college and university presidents, wrote to Democratic and Republican leaders of the tax-writing House Ways and Means and Senate Finance Committees, urging them to “swiftly correct a mistake.”