One possible version: 

Dear Peter,

     How are things going? Now I'd like to tell you something about our out-of-class activities.

     Our spare time is full of interesting activities. We read all kinds of books in the reading-room whenever we

have time. We've learned a lot more in this way. Among all the games, volleyball is my favorite and I often play

volleyball with my classmates. Sometimes we go in for social practice outside school. For example, we go to

plant trees in spring every year. We Can gain a lot of social experience and learn to work for the good of society.

I think out-of-class activities are quite necessary for us students. Through these activities we can learn a lot of

things that can't be learned in class.

     I hope to know more about your out-of-class activities. Looking for ward to hearing from you.

                                                                                                                     Yours sincerely

                                                                                                                              Li Hua