Chris Lehmann has a thoughtful post on The Seductive Allure of Edu-Tech Reform, which I agree with, but I don't think you have to think very hard to see that we're just looking at an investment bubble.
Let's take for granted that what ed-tech entrepreneurs are shooting for educationally are test score gains. If they're getting them at any scale, for real, consistently, with at-risk kids, we'd frickin' know about it, and truly, sales growth would be unstoppable.
Policy has already set the table for these guys with constant testing, carrots, sticks, etc. They just can't deliver!
The fact of the matter is there has been essentially no significant innovation in K-12 ed tech that actually solves our hardest problems.
Thus, we're looking at a hype bubble.