I had a classmate put a thermometer into the middle of a bunsen burner to “see how hot the fire was”. As glass and mercury promptly exploded everywhere, I’m pretty sure I saw the teachers soul leave her body. Never saw her look so horrified or pissed before.
I had a nun who taught us the famous quote 'Vini, vidi, vici'. I was also taught that this is where the evil 666 originated. (VI, VI, VI). It was only after an embarrassing conversation as an adult that I realized it was 'Veni, vidi vici'.
There are teachers - far too many teachers - purposely 'teaching' incorrect things such as sex education in order to further their radical and/or uninformed political-religious agenda.
I had teachers 'teach' us that certain musical progressions etc were 'incorrect'. When I pointed out multiple examples of these progressions in famous masterpieces, I was told that they were exceptions, and that they were still 'wrong/incorrect' etc.
I could go on. But my point is that given the state of teaching, it's no wonder some of the students struggle.
Oh yeah, depending on the age and experience of the student, putting a thermometer in a flame to determine its temperature is not an unreasonable thing to do. A teacher should have covered that before putting students - probably children - in front of an open flame.