At the start of semester, at one point I had 48 people signed up for my extension Algorithms and Data Structures course, which I said from day one would not last. (The extension class is for Distance Education students, offered by Harvard's Division of Continuing Education; students see recorded versions of the Harvard class lectures made available online, and I run the class very much like the Harvard class.) 17 made it through to get final grades. That's well within the normal range.
My reviews from the extension school have generally, over the years, been satisfactory. As I usually have minimal personal interaction with the students, I've never expected great reviews. Strangely, for the last two years, while my teaching review numbers for the regular Harvard class have significantly declined (due to a vocal minority that appears to not enjoy the class), the numbers for the extension class have significantly risen. Perhaps I should be concluding that I'm better on camera than in person?
Really, I'm at a loss to explain. Obviously, the extension reviews are from self-selected survivors, so they're more likely to appreciate the class. In the regular class, I notice that the poor reviews seem to come almost exclusively from those who are taking the class because it is (almost, but not really) a requirement for being a CS major -- hence, possibly, from people who don't really want to be there in the first place. I might think extension students have lower expectations, in terms of grades. For administrative reasons they really want to get at least a B in my class, and I think they're prepped to understand coming in that that's a difficult goal. I should point out that most -- indeed, nearly all -- of the 17 left at the end got a B or higher. Most also come in quite aware of the gaps in their background and work very hard to make up for them.
However, none of these things seem to explain the delta over previous years, and in particular the difference in direction in the delta between these two groups of students. Go figure.
In any case, the extension students from CS 124 this semester should be very proud of themselves. I believe my class is one of the more challenging undergraduate Algorithms and Data Structures classes at any university -- extension or otherwise. Many (most?) of these students have jobs, families, and other responsibilities that make taking any class extremely difficult. They should know that I'm impressed by them, and I hope my class turns out to be a useful experience for them.