For example, the proper usage of a teacher calling their student is -kun regardless of gender. But most of the time, female teacher use -san for female student. If a female teacher call their female student with -kun, then either she's pretty old or very traditional woman. This also apply to female senpai calling their female kouhai. (Ex. Tatenashi - Infinite Stratos)
A cold-hearted/spartan/hot-heated teacher is more likely to forego honorific for their students altogether. (Ex. Onizuka - GTO, Pin - Kimi ni Todoke, Chifuyu -Infinite Stratos)