Despite a growing interest in online learning among students, the availability of online classes in K-12 schools and districts hasn’t kept pace with the demand, according to a new report from Project Tomorrow and Blackboard Inc.

According to the report, more than 40 percent of sixth through 12th graders have researched or demonstrated interest in taking a course online, but only 10 percent have actually taken an online course through their school. Meanwhile, 7 percent of middle school students and 4 percent of high school students instead have pursued opportunities outside their school to take online courses–underscoring the disconnect between the supply and demand for online learning in today’s schools.

What’s more, a majority of school principals, 58 percent, say the online classes currently offered in their districts are primarily for teachers; just 31 percent say the classes are primarily for students. Additionally, while a third of teachers have taken an online course for professional development–a 57-percent increase from 2007–only 3 percent of teachers say they’ve taught a class online, a number that has not changed in three years. Just 13 percent of teachers say they’re interested in teaching online, a considerable mismatch with the growing student desire to learn online.

The findings are included in the report “Learning in the 21st Century: 2009 Trends Update,” which offers a further analysis of data from Project Tomorrow’s Speak Up initiative, an annual survey that has collected and reported on the views of more than 335,000 K-12 students, parents, and educators in the United States about online education and 21st-century learning.

“While many of our nation’s K-12 schools clearly recognize the advantages of online learning and instruction in teacher professional development, there remains a lag in utilizing this technology for student achievement,” said Julie Evans, CEO of Project Tomorrow. “Educators must embrace these emerging technologies to enhance student learning and fully prepare today’s students for future success.”

School administrators cited funding and teacher preparation as key barriers to offering expanded access to online courses, with 22 percent reporting that online learning was not a funding priority in their district. Some administrators said their teachers are not comfortable using the tools (18 percent) or teaching online (17 percent), are reluctant to try (14 percent), or their school does not have the expertise to create online courses (14 percent).