1 or 2 lessons a week.
1 or 2 lessons a week for 10 to 20 weeks straight is a very big commitment of time and money. Especially when you add in practice time to work on what you learn each week.
I'm sure doing it would give big results, but not many people who have full time jobs can do this.
It would be a good thing if instructors talked with students before hand to discuss expectations, time frames and amount of practice time the student can dedicate to pool.
Then again, that might scare off a potential lesson "sale".