Two American studies have raised questions about quality and access in distance learning .
The College Board, the United States university association that administers the SAT college entrance examination, found that distance education using high technology excludes low-income students. And the Institute for Higher Education Policy said previous reviews had overlooked high dropout rates, shortage of online reference materials and other problems.
The warnings come as distance education has begun to take root in the US on a large scale.
"All this new technology growing out of the internet and computer-based technologies seems to be evolving so fast, and the pace of change is so rapid, that we don't have a grip on where it is going to take us," said Lawrence Gladieux, author of the College Board report.
"There is no question that the new technologies are going to enhance instruction and educational opportunity for many, but I worry that it will leave some even further behind and actually widen the gap between educational haves and have-nots."
The report says online education will be less accessible to poor students who do not have access to the internet, or who have not been adequately trained.
"While education is the great equaliser, technology appears to be a new engine of inequality," the report says.
Mr Gladieux said the government should play a role in making more computers and internet connections available to low-income students. A federal programme, E-Rate, provides incentives for industry to give equipment discounts to needy schools and libraries. But the scheme is in peril after telephone companies were found to be passing their share of the cost on to customers.
Meanwhile, the Institute for Higher Education Policy questioned whether distance learning in higher education is as effective as some studies have suggested. Reviewing 300 reports on distance education, the institute found that research has focused heavily on particular courses or topics and has not looked closely enough at the availability of online reference materials. It said the studies have failed to take into account the high dropout rates in distance education.
This report, too, examined the question of access, suggesting that if a substantial number of students fail to complete their courses "the notion of access becomes meaningless".
The studies come as distance learning is exploding, with universities, community colleges and private enterprise building stakes in the new education market. Individual states plan their own distance education programmes, foremost among them California's Virtual University and the University of Texas TeleCampus.