If you mean up at Mammoth, I can recommend Kevin Kuljerich, out of main lodge. About 6-7 years ago I was up alone for a week and decided to take a mid-week lesson, and wound up with Kevin with what turned out to be a semi-private for the afternoon. In a couple of hours he brought me into the 21st century, teaching me modern ski technique with today's skis. There are so many out there using an 80s technique with new skis who would get sooo much more enjoyment out of their day if they could spend a few hours with a good instructor who is truly a student of modern technique. The key is "using all four edges you paid good money for". I have taken probably 150 days of instruction over the last 25 years, usually consecutive days up to a week in my early years with the sport. Lately, I have only taken the occasional single encounter when I have wanted to mix things up a bit, as I am pretty satisfied with where my technique is. That afternoon with Kevin was truly transforming. He was out for most of last season, as I had recommended him to a friend who said the ski school desk said he was out for the entire season. Bummer all around as they told my friend that Kevin is usually in great demand. However, I ran into him on Chair 2 (recognized him by the name tag, of course) in March and he explained that he had been recovering from surgery and was back at it. I expect that he is up there now.
I hope this helps.