When Penn State New Kensington decided to offer an experimental class that would offer extra help for math students, administrators predicted that about 70 students might actually enroll.

They were shocked then to see nearly double that number of students sign up for the one-credit "Math 97" class last semester.

Those eager for additional math instruction were students like Branden Citeroni, a trigonometry student and prospective mechanical engineer well aware of the steep slope of the road ahead of him.

"I hadn't taken many college-level math courses, and I thought, 'Oh man, engineering's based on math,' " said the 25-year-old junior. "I figured I was going to need some help."

The extra credit class is one of Penn State's answers to a thorny question confronted by universities nationwide: How do you keep students from dropping out of science, technology, engineering and math majors, known as the STEM fields?

Students majoring in STEM fields tend to struggle because high schools haven't prepared them well enough for college and professors stuck in a traditional large lecture format fail to engage students, said Ted Greenwood, program director at the Sloan Foundation, which awards grants to try to improve STEM retention.

An oft-quoted national statistic is that 50 percent of students who start off intending to major in STEM fields don't ultimately earn STEM degrees. There is little good national data on STEM retention, said Dr. Greenwood.

Data from local universities show that their numbers vary widely.

Of the approximately 200 students who entered Carnegie Mellon University's Mellon College of Science in fall 2007, for example, 20 transferred out, but 21 transferred in, giving the school a net gain, said Eric Grotzinger, associate dean of the Mellon College of Science.

At the University of Pittsburgh, about 65 percent of students who start in engineering graduate with a degree in that field, said Jill Harvey, coordinator of freshman engineering advising. An additional 10 to 12 percent graduate from Pitt, she said, but transfer to a different major.

And at the Penn State branch campuses, about a third of students who start out as engineering majors eventually graduate from Penn State with an engineering degree, a third graduate from Penn State with a different major and a third either drop out of school or transfer elsewhere. Those figures do not include students who started out at the University Park campus, for which engineering retention rates are above 60 percent.

The statistics on branch campuses led Penn State to apply for and receive a five-year, $2.4-million grant from the National Science Foundation to increase retention rates for students in the STEM field.

When the school examined the causes for the dropoff in engineering majors, it discovered that many seemed to have trouble moving through all of the required math courses, said Dhushy Sathianathan, head of Penn State's School of Engineering Design, Technology and Professional Programs.

"We are trying to provide resources and tutoring capabilities to intervene early," he said, noting that some of the students exit high school unprepared for even remedial math classes. "It's not their fault that they didn't have that preparation. It's not because they're not bright."

Several of the branch campuses are now offering the option for math students to take an extra one-credit course that functions partly as a study hall, partly as a tutoring session and partly to teach or reinforce study skills.

"If you're studying and something slips your mind, there's always a resource there," said Mr. Citeroni, of Penn Hills, who was so happy with Math 97 for Trigonometry last semester that he enrolled in it again this semester for College Algebra II. "Probably any math class I take from here on out, I'll take Math 97 with it."

In addition to the extra Math 97 class, Penn State is also using the grant to implement math pre-tests to get a fuller picture of a student's initial knowledge than may be evident from a wide-ranging placement test, said Dr. Sathianathan.

His focus is on retaining students who want to be engineers, but struggle with the coursework. But college students are notoriously fickle, and many leave STEM fields for other reasons, such as simple boredom or a newfound appreciation for another field of study.

In retention efforts, there can be a fine line between pushing students to do their best and pushing them to stay in a field that they might not find exciting. "We're not trying to convince people to do things they don't want to do, but we want to give them the tools so they can do what they want to do and be successful" said Lynne Molter, chair of the engineering department at Swarthmore College.

At Penn State, only one of every four new students is certain about their major as they enter college, and the rest report going in that they may change majors, said Michael Dooris, director of planning research and assessment.

Some data, in fact, show that students switch out of STEM majors at similar rates as they do other majors.

The National Science Foundation determined from longitudinal data from the National Center for Education Statistics that science and engineering majors "persist and complete undergraduate programs at about the same rate as non-S&E students."

The same report noted that enrollment in the science fields is bolstered by the social and behavioral sciences, which tend to gain students as they progress in their college careers. Some fields, such as math, computer science, engineering and physical sciences, tend to see undergraduate attrition.

At Penn State, the numbers on STEM retention at branch campuses are fairly similar to those of other majors. About 26 percent of liberal arts majors end up graduating from Penn State with a liberal arts degree, compared to 23 percent of science majors, said Dr. Dooris.

He noted, however, that some of the causes for transfers might be different. While engineering students might get stuck on a math course, liberal arts majors might discover college options that they had never even heard of before college.

Swarthmore, which has a grant from the Sloan Foundation, has hired a full-time employee to support and monitor its 43 engineering freshmen. The employee tracks their test scores and attendance, sits in on classes and arranges tutoring, if necessary.

In one recent instance, a student failed her first math test and the department immediately "rallied the troops," said Dr. Molter, setting her up with tutors and a faculty advisor. By the time of the next test, the student got a C plus -- still not ideal, but a great improvement, she said.

While there is sometimes a delicate balance between letting college freshmen be independent adults and wanting to help them, Dr. Molter believes that the college does more good by aggressively supporting students than by letting them fail.

"Students come in just not knowing the magnitude of what they need to be doing, the number of hours that are expected of them," she said. "The truth is, in any class, there's going to be a bottom quarter and that can be a hard thing to deal with."

Because Swarthmore students generally have been highly successful in high school, she said, sometimes they don't know how to ask for help when they need it.

Academic officials at Carnegie Mellon have noticed the same problem on occasion.They try to head off that and other academic or social problems with an advising program and student and faculty dinners to increase engagement. After first-semester grades come out, students with a grade point average below 2.0 are set up with faculty mentors.

At the University of Pittsburgh, the freshman engineering program also tries to ensure student success by making them feel like they are part of a community. Students take most of their classes together, have the option to live in special engineering housing and take a freshman seminar taught by upper classmen who have found success in Pitt's engineering program.

A committee of faculty and writing center staff also meets once a month to discuss issues with particular students or with the class as a whole.

"If there's a student who's struggling in a class, we know that from the faculty," said Ms. Harvey. "I wouldn't say we're intrusive, but we're definitely pretty hands on."