Teachers and classrooms are a staple of porn. That’s not really surprising given it offers a setting for a strong authority figure and a transgressive age difference. Also most people can remember a time when their hormones were gushing and there was a particularly attractive teacher that caught their eye. It represents a formative time for sexuality and fantasies.
Of course where you find classrooms, you also find blackboards and teaching notes. Spotting what porn creators choose to put on their blackboards can often be entertaining. Somebody even created a blog specifically for this topic, which features a quite ridiculous level of analysis. Typically the blackboards are full of random nonsense that looks somewhat academic. The example below is one of the few cases where the blackboard actually relates to the porn scene in question. There’s a scared looking semi-naked man with a collar and leash. I’m not exactly sure what the writing is, but I’d guess it relates to the best way to torture said man. That’s my kind of lesson.
This is from the Team Rinryu site.