The NSA has nothing on the ed tech startup known as Knewton.

The data analytics firm has peered into the brains of more than 4 million students across the country. By monitoring every mouse click, every keystroke and every split-second hesitation as children work through digital textbooks, Knewton is able to find out not just what individual kids know but how they think. It can tell who has trouble focusing on science before lunch — and who will struggle with fractions next Thursday.