When the class ended, Lisa immediately called out to me and told me to stay behind, using the excuse that I was the only one that was able to brew the potion in the entire class as a reason to talk to me.
The other students in the class thought nothing about it, chalking it up to Lisa discussing alchemy or something with me.
By the way, quite a number of them did not even manage to get the preparations done right, messing up at even the processing of the herb. It looks like it really would be a long time before one of them would succeed.
Lisa waited until the last student walked out of the class before she got up from her desk to go lock the door. She then pulled a lever by the side which also closed the shutters on the window, locking them in place.
"Ehehe~ Those are just in case a gaseous type of poison gets made inside the class and we can lock it in to purify it instead of allowing it to leak outside… It's also soundproof too~"