This is fairly basic idea, but I've seen interesting things happen often, so LET'S REVIEW.
Generally speaking, if you go to a syllabus-level group class (hello, "beginner group class", "community education ballroom dancing", "newcomer class", or anything with the words: Bronze, Silver, Beginning, Intermediate), there will be a few to many people (group classes often range from 3 - 50 people) attending. Some attendees will come as a couple and some will have come on their own. There will be ladies and gentlemen of all ages, but most participants will be more or less the same level of proficiency in dancing as you.
The teacher usually has a plan (God willing) in mind for which dance will be in focus, a particular "move" in that dance, and relative techniques they'll introduce and explain. There might be a quick introduction of the teacher and students and then you'll get down to work.
No matter the class material, at some point, I assume you'll be told to "find a partner", which is slightly horrifying whether you came with someone or not (or maybe that's just me, since I don't want to exclude anyone or play favorites or make it obvious I'm avoiding the person with bad personal hygiene).
Whether or not you came with a partner, grab whoever is closest doing the part opposite of you. Do it quickly, to facilitate more dancing in the long run. (Keep in mind that some ladies might be leading [ahem, like yours truly, the teacher] and some guys might be following, so if you're wondering, just ask, "Are you leading or following?" and grab appropriately.)
Once you dance once or twice with your first partner, your teacher will set up some means of switching to another partner and you'll dance through the selected pattern or technique again. And then you'll switch partners and do it again. And then you'll switch partners and do it again. And then you'll switch partners and do it again.
Now, if you came with a partner, you might wonder why in God's name you need to dance with anyone but your pre-selected sweetie.
WELL.
WHY YOU SHOULD SWITCH PARTNERS IN GROUP CLASS
COMMUNITY
One of the fun parts of ballroom dancing is meeting a bunch of new people.
Trust me.
Even as introverted as I am, ballroom dancing is a pretty chill way to meet a fairly diverse crowd of fun people.
If you don't switch partners, how are you going to meet any fun people?
LEARNING
Let's say you're brand spanking new. I PROMISE that dancing with someone who knows a little more than you (because maybe that partner has been to TWO classes before this one) will be exceptionally helpful. Even when that person who knows a little bit more DOESN'T SAY ANYTHING [warning side eye to slightly more advanced dancers in classes] and just dances the material to the best of their ability.
You'll also feel the slight differences in dance frame and muscle tone and partnering connection from each partner and learn what feels right to you.
And unless you're crazy and in need of intensive social conditioning, you're not going to argue with these nice people you barely know about their noodle arms or their lack of timing (which I totally hear you muttering to your usual partner), so you'll concentrate on what and how YOU can improve, which is also exceptionally helpful to your learning curve.
CAMARADERIE
As you rotate through all the fun follows or lively leads, you'll find out everyone's in the same boat, learning-wise. Maybe you can whisper, "Where the heck is my 'center'?" and find out no one else knows or you can be working in the mirror and discover everyone looks a little ridiculous trying to coordinate their arms with their Latin motion at first (and it's not just you).
You can be relieved when someone finally asks the questions you've been wondering (because at least 50% of you are wondering the same thing; again, trust me) or the teacher addresses some issue you've had and six toher people around you go, "Oooooooh."
It's a fun boat you are in.
TEACHING
If you're taking your first class or your hundredth, something about the way you interact with each partner is teaching that partner something. Yeah, sometimes, it might teach your partner how to move their feet faster so they don't get stepped on, but sometimes it might be how to dance a nice, 2-count "slow".
WHEW
If you did come to class with a built-in dance partner, by the time you get back to them, you will be relieved. No matter how good your other partners are, it's not too shabby to dance with your other half. And by that time, you'll know what you're doing!
In other words, please switch partners when you go to a group class. It's glorious in so many ways.
Three years ago: Dancing On the Fringe
Six years ago: LLLL