alt Hacker News> off the shelf eeg
We know that mild stress can narrow focus and help learning. "Neural connections do form when you struggle." [0] A little stress is not only good but necessary for learning while a lot of stress causes a breakdown. The trick is being able to judge the stress level of the student and every person is different.
The idea of using some type of bio metric data from EEG or blood pressure sensors will help determine a little struggle from a lot of struggle in formative assessment.