At Duology, we do private and semi-private tutoring a little differently than other companies. By joining Duology semi-private sessions, students can get better results even compared with conventional private tutoring, all for the cost of a prep course. That's a bold claim. Obviously, traditional private tutoring offered by our competitors is not completely ineffective, but it is so inefficient that Duology can produce better results even in a small-group setting.
How? Because tutors' time is expensive and limited, they often try to cover too much advanced material in one session. Retention drops off dramatically during the course of the session.
Optimal learning requires brief lessons on a new concept followed immediately by enough practice to master the concept. Unfortunately, most tutors don't sell their time in 5-minute increments.