Are high school classes like freshman, sophomore, junior, senior proper nouns?
The classes of freshman, sophomore, junior, and senior are common nouns, not proper nouns.
- Common nouns name general things, and do not require capitalization.
#rarr#waterfall, man, month, restaurant
- Proper nouns name specific things, and require capitalization.
#rarr#Niagara Falls, Walt Disney, March, Bob Evans
Since freshman, sophomore, junior, and senior are not capitalized, they are common nouns.
Here is a video on common vs. proper nouns that is helpful to watch.