Obelysk This is just a "maybe you could take a peek at this in the debug": for Sex-Ed, is your school debauched enough? Would make sense for the school to have a Lust/Corruption requirement to trigger the quest. I remember some time ago I had Theoretical going, and one of the teachers (Carmen?) walked up to me and said something along the lines of "I think the lessons are lacking, it feels like the students something more, but I cannot figure out what", which also had me stumped because nothing ever happened afterwards despite having cleared the blackmail chain for Samantha. Of course that was a save where I was keeping Corruption low ( <10 after almost a year).
Without looking at it myself, I would surmise that Practical would need at least three things: Samantha corrupted, the school corrupted to some degree (pure guess: 50+, you ARE about to "legitimize" sex, after all) and whatever prerequisite policies it has. And lastly, of course, have PTA corrupted enough to actually support it.
Futa cure: are those not locked behind Chemistry levels, as well?
UPD: I took a peek at the SexEd thingy myself, and from what I understand:
1. School needs to be at >40 Corruption and Lust; this check has a 6-day cooldown.
2. Samantha has to be teaching Theoretical SexEd; this check has a 6-day cooldown.
3. Her Corruption needs to be >70; this check has a 2-day cooldown.