Dear Mr Smith：

I am the organizer of an engligh speech contest   In our school 。   

  It is a great pleasure for me to have a wonderful choice to put pen to paper and invite you to be a judge. 

I will tell you details about the contest。

To begin with，the time of contest is at next weekend。

Secondly，It will happen in Our school。thirdly，the topic is “should students learn law”。

as a result，10 students will do an engilsh speech。

thank you for your consideration，and i am looking forward to your reply and agree。