Fall 2008 online enrollments were up 17 percent from a year before, with about 4.6 million students taking at least one class online, according to the 2009 Sloan Survey of Online Learning.

With all higher education enrollments increasing only by 1.2 percent for the same time period, the share of students taking at least one course online reached 25.3 percent. As recently as fall 2002, not even 10 percent of students were taking at least one course online. The data reflect nearly 4,500 colleges and universities, with information gathered by the Babson Survey Research Group and by the College Board, and supported by the Alfred P. Sloan Foundation.

While the trends outlined in the survey are clearly positive for advocates of online learning, they also point to lingering challenges. A survey of chief academic officers indicated the growth in online enrollments has not been matched by consistent training programs so faculty members can learn how to teach virtually, and that many of these officers doubt that their faculties truly respect online learning.

The doubts appear to be greatest at private nonprofit institutions and least in for-profit higher education. (While this survey relied on chief academic officers to evaluate faculty attitudes, other surveys -- that have asked professors directly -- have found faculty doubts about online education, especially about whether institutions are serious about providing support for those engaged in it.)

Here are the numbers on enrollment growth, with online enrollment referring to every student who takes at least one course online.

Growing Online Enrollments, Fall 2002 to Fall 2008

Despite that growth, the study also found that there is no assurance that faculty members are being trained to teach online.

In the survey of chief academic officers, they were asked (for the first time in the Sloan study) whether they provide training to those teaching online, and 19 percent said that they do not provide any training. Of the remaining institutions, many provide training in multiple forms, including internal training courses (at 65 percent of institutions) and informal mentoring (at 59 percent).

The chief academic officers were also asked whether their faculty accept "the value and legitimacy" of online education, and the results suggest something short of a strong endorsement of virtual learning. In the fall of 2009, only 30.9 percent of chief academic officers said that their faculty members do have such respect for online learning, while 51.8 percent were neutral and 17.3 percent disagreed. When asked two years earlier, a larger share of the chief academic officers (33.5 percent) agreed that their faculty members accepted online learning and a smaller share (14.6 percent) disagreed.

The Sloan report asks of this drop: "Does this recent drop indicate that the upward pressure to offer more online courses and programs that these institutions are experiencing is leading to increased ‘push back’ among their faculty? Future studies will need to track these results, paying particular attention to any possible relationship of perceived faculty acceptance to the rate of growth of online offerings at the institution."

The overall numbers of chief academic officers who believe their faculty endorse online learning would be lower if it were not for community colleges and for-profit higher education.

Percentage of Chief Academic Officers Reporting Their Faculty Accept 'Value and Legitimacy' of Online Learning