Having taught for several years, I agree that this is part of it. A much bigger reason is the need to avoid or reduce distractions. A class of 30 students all g

Having taught for several years, I agree that this is part of it. A much bigger reason is the need to avoid or reduce distractions. A class of 30 students all going off on separate tangents unrelated to the lesson plan, or unrelated the subject of the class, is unmanageable.