You do

Your grad-student's merciless tickling drives the young woman beneath you to an even greater level of desperation as she tongues your arsehole frantically until the sight of her suffering stirs your passion to the point that it becomes impossible to delay your satisfaction any longer.

"Well done, Skylark," you say, signalling the end of the test and standing up. Bethany sits back on her haunches, disappointment etched on her lovely face, whilst the blonde lies on her back, gasping for breath. "Now," you continue, "show me what you've learned about pleasing a man."

Bethany starts clearing up without a word, although you can tell she feels bad about letting you down by failing to break the will of the elfin teen about to service you. Skylark, meanwhile, rolls over onto the floor, where she kneels, kissing your feet and begging to be allowed to take your manhood into her mouth. You'd normally go somewhere more comfortable for this, but you need relief immediately, so you sit back down and invite her to begin.

The young beauty engulfs the head of your dick with her pouting pink lips, swirling her tongue across its surface before smoothly sliding it down her unresisting throat until her nose is buried in your pubic hair. You groan and throb with arousal. The training you've been giving her is certainly paying off and you don't expect to last much longer, but she seems to sense this and slips back off your prick with an audible pop to ask how you want to use her.