Yes, that’s true if other families/students agree to follow what you think.USB-C headphones are also easy to get/replace, so that argument doesn't hold water. And why does a school have to buy new iPads if they already have them? They can continue to use their existing ones for at least a few years for sure.
Again, I'm not on Apple's design team nor privy to their development timeline, so you'll have to ask someone at Apple who knows if you want all the details of why they make this or any other design choice. I can guarantee you, however, there's a logical reason (probably multiple) and it's not "hey, let's make some people angry just for the heck of it."
You literally have two very simple options (dongle or USB-C headphones) to continue to use wired headphones with all the newest generation iPads.