Nathan, 17, hasn’t even finished secondary school. But when he graduates this spring, he’ll already be halfway to a university degree.

A student at Lawrence High School in Fairfield, in the sparsely populated US state of Maine, Nathan is part of a fast-growing movement that allows secondary students to simultaneously enrol in university courses, getting a taste of higher education while earning credits that can save them time and money later.

Eight in 10 US high schools now offer university courses of some kind, reaching more than 4 million secondary students annually, according to figures from the National Alliance of Concurrent Enrollment Partnerships (NACEP). That’s about one in 10 high school students and a fivefold increase in just the past decade, the US government’s National Center for Education Statistics reports.

The idea is variously described as dual enrolment, dual credit, concurrent enrolment and early college. Whatever it’s called, research shows it is not just saving students time and money - it’s also giving them the self-assurance to go on to university, stay there and graduate in higher proportions than their peers who do not have access to higher education courses at school.

“I didn’t think college was even going to be an option, for financial reasons,” says Nathan, who will be the first in his family to go to university. “The fact that I’ve had this opportunity has added to my confidence a lot. I feel like I know what I’m going to do, that college is accessible.”

As reported in TES last week, schools in the UK are beginning to forge closer links with higher education. One comprehensive - Woolwich Polytechnic School in south-east London - is to offer degree courses in maths from this September, making it the first school in the country for 11- to 21-year-olds.

Most university-level courses in US high schools are taught under the supervision of a higher education institution by regular teachers who have master’s degrees or advanced education in the subjects. For other courses, students go to university campuses and learn alongside classmates of traditional university age.

“They learn what a bursar is, how to get to the book store, when to go to the tutoring centre, and all those pieces that can make going to college so confusing,” says Gretchen Ross, chair of the guidance department at Lawrence High, which offers a combination of in-school and on-campus courses.

Since the programme began in 2007, the proportion of Lawrence High students who go on to university has risen from about half to more than 80 per cent - much higher than the state average of about 56 per cent. “One of the ideas behind this was to increase student awareness that they have college potential,” Ms Ross says. “And the parents then see potential for their kids.”

Research consistently confirms that dual enrolment increases university matriculation and completion rates, especially among first-generation students such as Nathan and among low-income and ethnic minorities, who are the fastest-growing demographic of prospective university-goers.

“Low-income young people and under-represented youth from racial-minority backgrounds don’t know what to expect about how to navigate the college environment, how to get admitted, how to pick the right courses and pathways towards a career,” says Joel Vargas, a vice-president at advocacy organisation Jobs for the Future.

Only about half of low-income high school students end up at university, Jobs for the Future reports. But two-thirds of students who take dual-enrolment courses while in high school go on to earn degrees, according to the National Student Clearinghouse, which tracks enrolment and graduation rates.

“It’s not just changing their mindset. It’s changing their confidence, because they have actually completed college courses,” says Clarisse Haxton, senior researcher for education at the American Institutes for Research, which has closely tracked the dual-enrolment movement.

This kind of confidence-building seems to be what makes dual enrolment so effective among students who appear least likely to succeed, although the programme also serves academically gifted students who have outgrown high-school courses.

But the idea has had growing pains. Nathan’s rural district and some others notwithstanding, dual enrolment is more likely to be offered in affluent, suburban school systems where high numbers of students already go on to university, according to studies in several states.

Some of the programmes charge for tuition and books, further widening the socio-economic divide. Students at Lawrence High who take courses on the campuses of nearby universities have to pay part of the cost, although it is waived if they are from low-income homes.

High schools are increasingly having trouble finding teachers who are qualified to run the courses; at Lawrence High only a fifth of the faculty have master’s degrees. There are also concerns about the quality of courses taught by schoolteachers.

And although students can cash in the credits they’ve earned at their school’s partner university, there’s no guarantee the credits will be accepted by any other university they may choose to attend instead.

But the dual-enrolment trend shows no sign of weakening, largely owing to the fact that it can shave as much as two years off the time it takes to earn a bachelor’s degree - and cut the cost by up to half. At Lawrence High School, about a quarter of its 650 students are dually enrolled this year and will earn a collective 815 university credits worth $154,000 (pound;101,000).

“If you’re uncertain of your ability to succeed in college and you have this early opportunity to try it out, it gives you that moment when you say, `Gosh, I can do this work - I am capable of it,’ ” says Adam Lowe, executive director of NACEP, which is seeking to standardise and accredit dual-enrolment programmes.

“It’s an opportunity to role-rehearse, to have that early experience while you’re still in the supportive environment of your high school. There’s still your social network, someone who will call when you don’t show up for class,” he adds. “And it all comes before you’re enrolled [at university] full-time, and paying for it, and have moved away from home - before it’s really high stakes.”