Looking for this bdsm story about two students who started switching

[schaakzet]

I am looking for a story I read several years ago. I can't find it anymore. It was about two college students who switched. He gets to Dom her first, after that they switch. She is more experienced then he is, he learns after she tied him up.

Does anyone now this story? I think it was in 3 parts.

Thanks in advance!