Dirty stories written by the nine- year olds

These are the stories that were written by my students. They did it in teams and most of the them are nine. It might be O.K. for nine- year- old foreign kids to write this kind of stuff, but not for Chinese kids. Absolutely not. Andy and I were killing ourselves laughing when they were reading them.
The grammar isn't prefect but that's understandable. I don't know what to say. Should I be proud of them or... ashamed for them?