Snape is a worse teacher than he is a bully and the Half Blood Prince book proves it
I keep seeing people defend Snape as a good teacher just because he knows a lot about potions. Nah. He is actually terrible at teaching and the Half Blood Prince book makes it super obvious.
In Half Blood Prince we get Snape’s old textbook and he has rewritten a bunch of the recipes to make them way easier and better. Harry who never cared about potions suddenly does better than Hermione who has been top of the class for years just by following those notes. So Snape clearly understands the subject on a deeper level than the actual textbooks.
But when he is teaching? He walks in, writes the basic book instructions on the board, and tells everyone to get on with it. No explaining why anything works. No tips. No helping when people struggle. Nothing. If he used even a fraction of the simplified methods from his old book the whole class would have done better. We know he never did that because Hermione reads every textbook cover to cover before term starts. She would have noticed if Snape’s board instructions were different and easier. She never says anything about it across all those years.
Instead of teaching he just bullies. Neville messes up one step and Snape threatens to poison his toad. That is not teaching. That is just being an asshole. Students are supposed to make mistakes while learning. Why does he act like everyone should already be perfect the second they walk in?
Honestly what is even the point of his classes? Anyone can sit in the common room and follow the book. A teacher is supposed to explain things, correct mistakes, and make the subject clearer. Snape does the opposite. He has the knowledge but refuses to share the good versions and would rather mock people than help them. Knowledgeable does not equal good teacher.