A version of this post titled “AltSchool’s education experiment” originally appeared in Data Sheet, Fortune’s daily tech newsletter.

Last week I visited AltSchool, the San Francisco-based education-technology firm that has begun its corporate life by operating a small number of private “micro-schools.” AltSchool’s CEO, Google goog veteran Max Ventilla, explained why his toddler of a startup—it began in 2013—began with baby steps. Other “ed-tech” companies have tried building broadly applicable technologies to achieve incremental growth. Almost all have failed. By beginning with small schools, Ventilla said, AltSchool can aim revolutionarily for the middle ground of teacher autonomy and accountability.

In other words, it can experiment. “We’re kind of flying the plane while we’re building it,” Ventilla said. This is a tried and true cliché of Silicon Valley product development. The old way, think Microsoft msft , was to tinker for years on complicated software and then ship it at once. The new way, think Facebook fb , is to iterate and then ship frequently.

The difference is that AltSchool is experimenting with the lives of children, not a better way of tagging beer-bust photos. The reason the plane-flying analogy amuses is that no one in their right mind would tinker with an airborne plane. Yet AltSchool asks parents to pay for the privilege of supplying their children as guinea pigs.

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Some of what it is doing is fascinating. AltSchool has raised $133 million, and it has developed unique technology that borrows from current tech-industry memes. A student “playlist” shows all the topics and tasks accomplished. This not only allows a teacher to focus on unknown areas but also, cleverly, avoids wasting a child’s time rehashing completed material. A “parent portal” provides a stream like Facebook’s News Feed to keep parents up to speed on their child’s progress.

I’m intrigued by AltSchool, and my biggest gripe, which I shared with Ventilla, is that he’s not applying his energy, smarts, and vast amount of available capital to improve public schools, especially in San Francisco. He hopes the company’s “platform” eventually will be available to public schools.

Rebecca Mead’s meticulously reported feature in the current issue of The New Yorker, “Learn Different,” discusses this and many other pros and cons of AltSchool’s approach. I highly recommend it if you’re half as intrigued as I am.