The film, titled "Grey Matters," is on schedule to be completed by the end of next year by Persaud's company, Change the Lens Productions. Persaud said she is financing the independent feature through a crowd-funding campaign and through grants.

Her first film, "It's a Different World," which followed three children with autism, was produced with the National Film Board of Canada and distributed by the Filmakers Library in New York.

Alejandra Whitney, a fourth-grader who transferred to Roland Park this year and will be part of "Grey Matters," said she first noticed that the "classrooms are bigger" than at her former school. Then she discovered that her new classmates check homework together, "instead of just the teacher checking it."

"Some of the things I'm learning here, I learned them already," she said. "But they're much funner. Like when we read the book together, instead of separately."

Another student in the documentary, Josiah Johns, said he thinks Roland Park is fun "because we get to learn more stuff, and I can feel myself getting smarter."

For example, Josiah said, his lesson in Holbrook's class about erosion taught him something new.

"I didn't know that water could do that, even though I saw it at the beach," said the fourth-grader, in his second year at Roland Park.

Holbrook, in his fourth year of teaching, said he feels he has reached his goal as a teacher when "kids learn and they don't even recognize it." And the model allows him to do that, he said.

The model also taught him to use approaches with students, such as humor, that he overlooked in his first two years of teaching.

"The first two years as a teacher is like trial and error," he said. "But if you have something laid out for you, with research behind it, it helps to organize your brain. The type of planning that goes into this is exhausting. But once you do that up-front, it's good."

Many students, he said, are "taking risks and putting themselves out there to absorb this stuff from you, so you have to do that, too.

"And when everyone is comfortable, you can see their little brains humming."