Middle-income families — those earning between $35,000 and $100,000 — spent $21,347, a decrease of nearly 6 percent.
Low-income families, with income less than $35,000, saw their costs go up 14 percent to $19,888.
One reason for the increase for low-income families is that they switched to less expensive schools a couple years earlier and now are experiencing tuition increases there, says Sarah Ducich, senior vice president of public policy at Sallie Mae.
And more low-income students attended school full time last year, the survey found, rather than going only part-time to save money.
Parents also are relying less on tapping 401(k)s to pay for school — another good sign. Saving for retirement should come before college. That's because there are loans, scholarships and grants for school, but no such money for retirement.
More families are applying for financial aid instead. Sallie Mae reported that 80 percent of families filled out the Free Application for Federal Student Aid, up from 72 percent the year before. The uptick was largely from middle- and high-income families seeking assistance.
And they're getting aid. Grants and scholarships made up one-third of the funds used to pay college costs, up from 23 percent the year before.
This, too, is good news, because for years many families didn't fill out the FAFSA form, figuring they wouldn't qualify for aid. In reality, they were leaving money on the table.
Sallie Mae also found that parents were less inclined now to stretch themselves financially to pay for college. A survey released last week by Fidelity Investments reported that parents expect more sacrifices from their college student.
About half of the more than 2,300 parents polled by Fidelity said they are having a child live at home while attending college, and 44 percent said they encouraged children to attend a public school. Forty-six percent are asking students to help pay for college and 44 percent want children to graduate in fewer semesters.
And two-thirds of parents say their students must get at least a B average if they want mom and dad to foot the bill.
Officials at some Maryland public institutions say they've noticed these trends.
"Parents are putting a value on their own funding. It's like merit aid," says Sarah Bauder, assistant vice president for financial aid and enrollment services at the University of Maryland, College Park. "We see it all the time and have kids who didn't get a 3.0 come in and say, 'Mom and Dad won't pay.'"
Bauder says 30 percent of federal aid forms at College Park are now filed by high-income families, compared with 16 percent four years ago.
Howard Community College has seen its enrollment jump 75 percent in the past decade, to 9,568 students last fall.
Barbara Greenfeld, associate vice president for enrollment services, says the school's honors program attracts students who otherwise would attend a four-year institution. But price is a factor, too.
"These days, even if you can afford it, the idea of saving $50,000 is appealing," Greenfeld says.
As long as the economy languishes, families are likely to remain price-sensitive. And they soon will have another tool to weigh their choices.
In October, colleges must starting posting a "net price calculator" on their websites so families can see what they likely will pay to attend a school based on their financial circumstances, says Pauline Abernathy, vice president of the Institute for College Access & Success.
"It's a way for people to make more informed decisions," she says. "They may find the school with the higher sticker price would have cost them less than another school with a lower sticker price."
Families could discover they can afford pricey Harvard — nearly $53,000 a year for undergraduates — thanks to aid and tuition caps for low- to moderate-income students.