Was reading this for old times and I almost forgot this one hentai series named Xtra Credit. One scene had the main character, a teacher, needing to go to the toilet because to take a dump. She was about to enter a stall when one of her students was inside. She give him a blowjob while trying to hold in her poop. She couldn't hold it in anymore, so she shoves the boy away to use the toilet. The boy says that he wants to see her do it, so she ends up pooping in front of him.