Maryland students who default on federal college loans tend to be poor and drop out of school before earning a degree, according to a new state study that provides the first insight into the type of student responsible for a rapid escalation of unpaid student debt.

More than half the students who failed to repay their loans had gone to for-profit trade schools, although these so-called proprietary schools enroll just one-fifth of Maryland's postsecondary students, according to figures compiled by the State Board for Higher Education.

Graduates of the state's public colleges and universities seldom default on their loans, the study found. While 12.5 percent of Maryland's students have failed to repay loans, just 1 percent of the public college graduates have fallen into default, according to the state figures.

The profile, based on an analysis of the 13,000 Maryland students who have defaulted on Guaranteed Student Loans since May 1986, was released this week. It emerges at a time when educators and politicians have become increasingly troubled by the burgeoning volume of unpaid debt in the federal government's chief form of financial help for college students.

Loan defaults drew widespread attention in September, when the first national study of the 22-year-old GSL program found that about $5.6 billion in loans had fallen into default, including $71 million in loans from Maryland. Under the federal rules, a loan is considered in default if a borrower falls four months behind in payments.

The issue took on greater immediacy for states in November, when U.S. Education Secretary William J. Bennett announced that the Education Department was taking the first steps toward cutting off all new federal loans and scholarships for students at some schools with a default rate of more than 20 percent. The punishment would be the first attempt to hold schools responsible for defaults on the loans, which are made by private lenders with the backing of the federal government.

Currently, the default rate exceeds 20 percent at 30 of the 101 Maryland colleges, universities and trade schools that participate in the Guaranteed Student Loan program. The vulnerable schools include Bowie State College, Montgomery College, Prince George's and Howard community colleges, and Morgan State University.

Sheldon H. Knorr, Maryland's higher education commissioner, said cutting off aid would be disastrous for such schools, because they tend to enroll low-income students who depend heavily on federal help to afford college.

The U.S. government provides 80 percent of all financial help to Maryland college students, he said.

In an attempt to ward off such penalties, Knorr appointed a task force late in the fall to try to devise ways to bring down default rates. The statistics were prepared for the group, which plans to release recommendations in the spring.

Until recently, educators and politicians in Maryland and elsewhere have debated whether defaulters were simply shirking their financial obligations, or whether they didn't have the money to pay their college debts.

The Maryland study suggests that, compared with other college students, defaulters are poor. Their average income, as calculated on financial aid applications, is $10,700, and half of them receive no financial help from their families.

"The biggest reason {for default} looks like it is economic," said William Broder, a member of the state higher education board who is chairman of the task force. He said the finding supports criticisms that the loan program, originally conceived for middle-income students, has been extended to too many students who lack a realistic chance of being able to repay their debt.

The study also found that three-fourths of those who defaulted dropped out of college.