For years, frequent flyers have used their mileage-earning credit cards to pay for their kids’ college. And why not? With today’s tuition costs, it is easy to earn one to two free tickets a year using this strategy. But according to a story recently in CollegeJournal from The Wall Street Journal, this practice may soon come to an end, with more colleges and universities refusing to accept such large payments by credit card.

The reason — economics. Most of these institutions are hit with a merchant fee averaging about 2.2 percent. Given that college tuition averages $25,000 a year, this is a lost revenue of $550 per student. The article noted that the University of Texas paid over $3 million in credit card transaction fees last year alone, and is among the many schools looking for solutions to this problem. As you might guess, some schools will begin to assess a service fee of around 2 percent if parents want to continue to use credit cards to settle the tuition costs.

WORD TO THE WISE: Be prepared to ask about these service fees before paying with plastic. At a cost of 2.2%, you’ll probably end up paying more to cover the service fee than the price of an airline ticket.

TIP: Visa does not allow surcharges to be added to a cardmembers charge, so choice of card may be your answer if your school of choice follows this trend.