First year physics is mostly review for a lot of incoming freshmen, especially if they did one or more AP classes in high school. I'm not suprised that some would do great even skipping the lectures.
When did they put freshmen on grades? When I was at Caltech years ago, first year was pass/fail.
Back then, Goodstein taught phys 1a. Fine lectures, unless you had read the chapter in advance. Then you noticed that his lecture was almost identical to the text, which made it hard to stay awake. Oh, and the retch session were taught by full profs, not grad students, so a lot of learning happened outside of lecture.
Highly qualified students have the option to test out of the different terms of Physics 1. (I know because I graded the placement tests for five years.) I suppose some of them take the course anyway to get an easy A, but this guy I'm talking about aced Physics 1c analytical track, an E&M course that uses Purcell, and very few high schools cover material that advanced. (It's well beyond even AP Physics C material.)
Regarding grades, here's how it shakes out nowadays:
Shadow grades don't appear on your report card, and they don't count towards your GPA, but they are used for internal scholarship awards and recommendations.
Recitation section TAs in physics have been a mix of professors and grad students for as long as anyone can remember. Virtually without exception the best TAs were grad students (as measured by student reviews, section sizes, and exam results), though some of the professors weren't bad either. This jibed with my undergrad experience at Harvard: almost all my physics professors sucked, and by far my best instructor was the 22-year-old grad student who taught my freshman physics section.
When did they put freshmen on grades? When I was at Caltech years ago, first year was pass/fail.
Back then, Goodstein taught phys 1a. Fine lectures, unless you had read the chapter in advance. Then you noticed that his lecture was almost identical to the text, which made it hard to stay awake. Oh, and the retch session were taught by full profs, not grad students, so a lot of learning happened outside of lecture.