Epic, there are different criteria in what I considered a good lesson, I'll mention some of them from my experience, factoring in that the SS director was my best friend for many years even before we became instructors.
Tipping can play a role. The director came to me one February and said that he will give me a private but it has to be on the sly.
An industrialist from Cleveland who was known as a real heavy tipper had been taking once a week lessons from Joe. The director thought that he hadn't advanced much and asked the customer who said that all he was doing with Joe were excerzises.
The director thought that I could do much better with him but he was afraid that instructors would think he yanked him from Joe so I, as his friend, could reap the dollars. So he waited until Joe was out and then told the guy to go out with me.
That man had been ready for a break through for some time but my suspicion is that Joe milked him. In two lessons the man was doing linked fall line turns. Joe hasn't talked to me since nor any more than necessary to the director.
A funny one that got me in trouble with the rest of the staff was when four gorgeous models from an agency came out to try skiing. Every male instructor in the lodge did at least one walk-by while they were getting ready, some helped them with their boots, others told them to ask for them at the desk, etc.
Then the SS director came out and said loud enough for the instructors to hear: "Ott is still finishing up a lesson but he will be in to take you out soon". The murmur and snide remarks as I came in to take them out were viceous.
What's funny about it is that those were models I had used in fashion photos (I was a photojournalist/Knight Ridder) a number of times and it was me who asked them to come out and try skiing.
Well, their legs are valuable so we did just a little sliding around and then went to the bar (sans jacket) and had a good time. I explained later to the few instructors who confronted me, but many others thought that the director gave them to me as a friendship gesture.
But what I really consider a good lesson is one where we don't stand around doing a lot of talking, but rather ski and correct.
In the 60s and early 70s there were only few full-certified/level-3 instructors and we got the advanced students, who seldom show you a gleem of satisfaction. They mostly are forever dissatisfied and grumbly because they think they should be doing better than they are.
When a skier comes and says that he can make this turn one at the time or maybe link three of them but he can't sustain the links and you get him to now be able to link them all, he bitches because he thinks he should have been able to do that all along
But getting a kid to make the first solo run down the bunny hill without falling can also be classified as a 'good lesson', but after the fact.