When I was guiding I would quite often explain to clients that they will get way more education per dollar spent in a private or semiprivate day than in a group lesson.
I teach aid climbing at two people at the same time....annoying because it is so slow that....zzzz...you berely....zzzzzz.... stay ......awake.....zzzzz...... between two mistake that the climber do. More people means more action for the guide who have to look at what people do at every moment (in the nose, Yosemite, a climber lost his thumb because he place his finger at the wrong place).
So, I think that for the goal to reach, learning how to place good pro, it is a good ratio. But, if the goal is to know the level of stress I can sustain, without having an anormal reaction, a one to one ratio is better -In diving, there is a test like that. You dive and your guide keep the bottle of air for him and he keep you under the water level for a while to see if you can keep your calm in a very stressfull situation, it is not very pleasant-.