The biggest difference in my discussion however, is that rather than focusing on educating future chemists, I'm going to speak to educating future chemical engineers, and there are some pretty big differences. Engineering classes typically don't start until the end of the sophomore year or early junior year. Junior year is pretty late in one's career to face a weed-out class and risk of changing one's major, but that is how it's still done. Keep in mind that at this point, the students have already survived the "weed-out" freshman chemistry class and now have to face their introductory "Mass and Energy Balances" class or something equivalent.
For those unfamiliar with the subject, it is mostly a matter of bookkeeping. You have a piece of equipment that has various mass and energy flows going in and out. The one and only equation you need to know is
"Accumulation = Inflow - Outflow + Generation - Destruction"You set up some linear equations and solve for the unknowns. There probably are some unit conversions too, but this is all just a matter of keeping the details straight. If a student can't handle this, they are really going to lose it when it comes to doing the same in fluid mechanics. In that subject, they have run similar balances with 3-dimensional, multivariable calculus.
When I was a TA, I never once was told by the prof that we had to cut a certain number of people or reduce the size of the class or hold the students to some arbitrarily high and/or capricious standard(s). It always seemed to me that students self-selected changing their major. And blaming it on a bad prof isn't too likely, as this initial stuff was pretty straightforward and intuitive. It's no different than balancing a reaction. Having a rotten prof for fluid mechanics and heat transfer is an entirely different matter. [*]
This all reminds me of the one episode where the prof in fact actually bent over backwards to pass a student. He was a senior who never did any homework and only came to class for the exams. I personally don't have a problem with such an approach IF the student still does well. But that wasn't case here. The student always had the lowest grade on exams. So come the end of the year, I recommended an F for him. Imagine my surprise to see that shot down. He got a D. The prof justified it by saying the school would be done with the student. He would graduate and never be on this campus or any other again. A Gentleman's D.
[*] I know. Been there, done that. And am still irate at the profs all these years later. And it wasn't just me. The Class of 1984 from Minnesota is the "Lost Class", the one that never provides news items to the Alumni newsletter or donates money. 30 years later and the anger is still there. That's how much a bad prof or two can impact hundreds of students.