If the structure of the class incorporates using real-world code, then fine. Most upper-division classes allow you to use any libraries you want anyway. But som

If the structure of the class incorporates using real-world code, then fine. Most upper-division classes allow you to use any libraries you want anyway. But some classes, especially lower-division, are explicitly built around learning a concept from scratch. If you copy the code, you can't learn the concepts. I agree that teachers should strive to allow "open internet" assignments and tests as much as possible, but it's not always viable. All the best classes I've had were this way, but it's usually quite labor-intensive for the instructors.