The benefit from 1-on-1 tutoring comes not just from finding what the student knows. There are any number of standardized tests that can determine that. Khan Academy does this for free and also adds lessons for mastery based learning.
The benefit comes from understanding how the student misunderstood a concept being taught to them and then fixing that misconception.
The benefit comes from understanding how the student misunderstood a concept being taught to them and then fixing that misconception.