A graphic used in a new online AP Calculus lesson. (Image by Patrick White, designer/Davidson Next)

The explosion of free online education, known mainly for targeting adults, is reaching ever further into high schools.

On Wednesday, a new sequence of lessons for high school Advanced Placement courses in calculus, physics and macroeconomics went live on a free Web site founded by the Massachusetts Institute of Technology and Harvard University. The lessons, developed by Davidson College for the site called edX, represent a new step in the evolution of ties between the popular AP college-level program and the “massive open online courses” known as MOOCs.

Other MOOCs in recent months have targeted AP students in subjects such as biology, computer science and chemistry. They aim to prepare students for exams that offer potential college credit for high scores. One philanthropist, Steven B. Klinsky, has even suggested that these MOOCs can help create a pathway for students to obtain a full freshman year of college credit for free.

[Donor seeks to offer ‘freshman year for free’ through online college courses]

Davidson’s sequence is a bit different. The private college in North Carolina teamed with the College Board, which oversees the AP program, and with high school teachers in the Charlotte-Mecklenburg area and elsewhere to develop online lessons in difficult topics. These lessons are meant to supplement live teaching, not replace it. So teachers and students can pick and choose what they want to use.

Perhaps it is best to think of them not as MOOCs, but as massive open online lessons, or MOOLs.

Why calculus, macroeconomics and physics? Davidson said there is evidence that students “have significant difficulty” in mastering the material from those AP courses “because it requires a combination of technical knowledge, precision and analytical skills.” The challenge is greater, the college said, for certain students “who lack access to high quality instructional content.”

Davidson designed the lessons based on College Board data indicating which topics are the most difficult. For instance, calculus topics covered include the “chain rule,” “implicit differentiation,” “L’Hospital’s rule,” “Riemann sums,” “parametric equations” and “series convergence.”

Here’s what Davidson calls a “macroeconomics concept map.” It shows the AP macroeconomics syllabus as an infographic, helping students and teachers understand how the new lesson modules fit into the College Board curriculum.

The project was funded by a $1.8 million grant from the Laura and John Arnold Foundation.

Davidson said that four of its faculty members, with long experience in the AP curriculum, edited the content of the lessons, including videos, interactive tools and assessment questions.

“We know that online AP courses have long been available to students who lack access to an AP teacher, but many students—including underserved and under-represented students—struggle to complete such college-level coursework on their own. This project helps to make equal educational opportunity real for all students,” Carol Quillen, president of Davidson, said in a statement.

This post has been updated.

Read more:

EdX turns 1. Now what?

Elite education for the masses

New Coursera chief stresses the ‘Wow’ factor for huge online courses