My stepdaughter is a pretty smart kid. She's in college now as a pre-med student and is working really hard to get good grades. I stopped in her room the other day to see how she was doing, and was caught a little off guard when I saw her with what appeared to be a very realistic fake penis in her hand! She was sitting on her bed, wearing her big glasses and knee high socks, and in her hand was an obscene looking fake penis that she was using to study male anatomy. She greeted me, and told me she was having trouble with this class and really wanted good grades, but the big fake penis was not really helping her understand how a man's body worked. She had a suggestion for me that really took me by surprise. She said that if I would help her get a good grade, her mom would be happy and would never have to know that I helped. She asked me if she could see my penis and thought that if she was able to take a sperm sample into class then she and her classmates could look at real sperm swimming around under the microscope, and she could get extra credit! Always the helpful Dad, I laid down on her bed and let her take my learning device out of my pants. She started by measuring the length and circumference of my cock and jotted her findings down on her notepad. This girl was being very scientific about the whole thing. She then began to stroke my penis lightly, examining how it began to grow in her hand. She was fascinated by how hard it soon became, and began to stroke it up and down to begin the semen extraction. She knew I would need some encouragement if she was to get a big enough load out of me, so she took off her top and bra and let me have a long look at her perfect breasts. She's a petite little thing, and her huge natural tits really started to get things flowing. I could feel an enormous load building, and I knew it wouldn't be long before I filled her little vial. When she removed her shorts and panties, she straddled my leg and began to grind her bare pussy against my thigh. She turned around to let me see her tight little pussy as she continued stroking. Before I knew it, I started spewing sperm all over her hand, overshooting her vial by a foot at least and splattered it all over my shirt. She scooped it up with her fingers and filled her vial. "Thanks Daddy, That looks like some good extra credit!"