I personally would prefer no classes.
That's because number one...as it is, in magic you get to learn from people! Whether you watch a video on YT or download an effect from TXI, or study from a book...someone is teaching you.
Second of all, magic is a bit unlike studies, because if you take Physics classes for example, a mnemonic to memorise the Laws of Gravity told to you by the teacher will work for you as well (93% chance). But how you perform tricks and how you don't, depends on the magician, and each magician has their own style!
But music and dancing, where each performer has their own style as well, aren't there classes held? Well...magic is a performance art. And going to classes may help develop the sleights, not performance. And that may produce many sub-par magicians too. You know, people might enrol because they think magic is cool, and then they leave the classes, don't pay attention. But they know the methods right? And THEORITICALLY, they are magicians! Perfect recipe for wannabe hecklers.
Now, maybe the classes encourage students to develop their own style? That is difficult, see...and that's why learning from books develops your performance more than any videos, YT or paid for downloads...because no matter how much of an aspiring magician you are, people have a tendency to copy fromthose whom they learn. So the students will be more inclined to copy the style of the teacher.
No...I support magic clubs more. Like, no teacher...but many magicians, novice or experts together. No payments, but there will be some teaching something, some discussing theories and a few friendly arguments about or against things going on in the community of magic. Will do much more good than classes I feel.
Also, there's the fact that the word 'classes' has a habit of ruining things. Now if you LOVE magic with all your might, and you can fight with people FOR magic, magic is your PASSION, if your trick fails maybe you feel like suiciding...then this won't trouble you. But have you seen how many people are like, "Oh I love singing" and as soon as they join classes, their interest and love lessens? Because the word 'classes' makes it seem like they HAVE to do something, it is kind of a routine thing then. Like, whether you are tired or not, feel like it or not, every Thursday seven in the evening a magic class?!? Hell no!
Then there is the fact of discovery. When you learn something and say, post your performance somewhere, people say it is great, and your audience loves it...won't it feel great to have only yourself and the creators of the effect to credit? Add "teacher'' to this equation and...you dunno how much annoying it is to write "Thanks to Mr. X, without whose help I would have failed" in the Acknowledgement section of all projects!
Also, maybe there is some regional bias involved in my reply too...because the level of magic of the magic classes here...I'd rather become a chef than join those classes (which is saying something seeing I dunno how to make a good cup of tea either, sue me). So if I sound a little too bitter, sorry.
But things like lectures, clubs, mentors, consultors, those are cool! But magic classes, er... not so much. FOR ME that is, other wise I clearly see the other option winning right now.
But if you are talking about Hogwarts, then it is a different matter altogether. I swear I was so sad I did not get the letter when I turned 11.
*hello darkness my old friend*