There are basically 3 sizes of classes.
The largest ones, in lecture halls, are the basic foundation courses that are common to many majors/disciplines. They meet twice a week for lecture with the professor 2-3 times a week with the huge group (120 -150 students?) and once a week for discussion section. The discussion section is anywhere from only 20-30 students, so it’s more personalized and is the opportunity to break down any problems or get more detailed explanations of topics raised in the lecture.
The medium ones are getting more into things specific to your major and have a similar meeting arrangement (sometimes with but mostly without a discussion section) but the lecture is typically 40-60 students.
The smallest classes are usually the highest level classes that are electives and can have as little as 15-20 students.
Of course, there are some exceptions, such as freshman English, that fall into the smallest class category. You should also know that the best profs are not reserved just for upperclassmen…you can read about the philosophy for the “keystone” classes here http://www.keystone.umd.edu/about
My son never mentioned class size as a problem for him because the discussion sections give the small size class opportunities to learn more difficult concepts. I will tell you that the key to surviving big lectures is to actually attend them (I’m being serious). That’s where students get into trouble - no one is taking attendance, so it’s easy to skip a class. Once you skip one, it’s easy to skip another…and so it goes.
My son’s secret to success as a student was always attending lectures. He may not have liked a particular class here or there, but he always went (at least that was his claim, lol). He is pretty disciplined, so I do believe it, actually. His strategy was to be actively engaged in a lecture (to the best of his ability), go back to his room and do his problem sets right away (instead of blowing them off like most students do) and then he was free for the rest of the night to have fun (which he did!)…students that put things off ended up with having to read the textbooks to learn what was taught in lectures. My son does not like to read, so he found attending lectures to be less painful than reading and a more efficient way to learn the material. Sounds simple and logical but you’d be surprised how much discipline it takes to attend class when you are away at school and mom isn’t around to nag, lol.
The other key to success is to really take advantage of professor’s office hours. It takes a while to overcome the high school mind set of not going to the teacher after hours, but going helps tremendously and profs really appreciate that students show an interest in doing well/learning the material. The profs at Maryland are generally very approachable and love to help students. They often give career advice as well.
Tell your daughter that there are always going to be a couple classes that are not to her liking but are required (I want to say it was dynamics or maybe thermodynamics that were my son’s biggest challenges?). MechE is very broad which is why it’s so popular - it can translate into a large variety of job options. Yes, MechE has the most number of students as well, but that also means more people to study with, and larger variety of electives to choose from.