When I was in elementary school, I had a teacher who made chumras into halacha. As in absolute if you don’t follow it you are going to burn. This included things like “wearing skirts to your ankles is totally assur!” and “tights must be worn at all time!”
When anyone mentioned their Rav held differently, she would scorn the Rabbi.
Kids see this and learn to disrespect their teachers.
That was a tough year – we clashed in many ways.