In a sign of a stronger economy, more young adults are skipping college and heading back to work.

College enrollment in the spring semester dropped 2 percent from the year before, to 18.6 million, according to a report being released Thursday by the nonprofit National Student Clearinghouse Research Center. The steepest drop was among students in their mid-20s and older who are re-entering the workforce. The report doesn’t examine whether students are dropping out or declining to enroll in the first place.

Hardest hit are community colleges, as well as for-profit institutions, which are shutting down amid government accusations that they inflated the job prospects of graduates. While more working adults are shunning higher education, enrollment of traditional students who go to college fresh out of high school was unchanged.

Those students “are staying enrolled, even at the most expensive four-year institutions,” said Doug Shapiro, executive research director of the group, based in Herndon, Virginia, which collects figures directly from colleges.

Declining enrollment presents a challenge to President Barack Obama’s goal of boosting the college attainment rate to enhance U.S. economic competitiveness. In January, he proposed making community college entirely free. Even though studies show a college degree tends to pay off over a lifetime of earnings, many students are worried about their higher education debt, which now tops $1.2 trillion.

More potential college students are favoring the short-term benefits of a job, rather than the long-term returns of college, said Jason DeWitt, the center’s manager of research services. “If someone has bills to pay, they may not have a choice in the matter,” he said.