Ann, you are correct, of course, but there are so many other variables that in the end it may not make a significant difference if a student uses the same enlarger. Bulbs age and change...so even the same enlarger will not give the same results over a period of weeks. Then there is the age and use of the developer, new packets of paper from different emulsion runs, age of the contrast filter, et al. But as much as I try to keep all the enlargers well maintained and aligned, each has its own "personality" and it does help to learn the quirks of the enlarger one is using (and also the timer that is tied to the enlarger)!
We have two banks of enlargers -- 23C's and D5-XL's. Students do tend to use one type over the other...and many students do have their favorite enlarger. But since we have 19 enlargers and about 125 students per semester, getting one's favorite enlarger is not a given on any open lab period.
Vaughn