Logic for recommanding content

Hi,

I'm from an ed-tech organisation in Vietnam, and we are trying to produce a version of Khanacademy in Vietnamese with the curriculum of our country. Although I do the same skill practice a lot of times (10 times) in your prep test SAT page, I can't figure out your logic of evaluating student's level (of that skill - Interpretting linear fuctions). I'm not sure it's appropriate, but could I ask for that logic, it'll help us helping children here, they don't speak english, and schools' quality is really bad.

Thousands thanks,

Best regards,

Tuan Anh NGUYEN