My 5 year is cussing at school!?

Ok.. my 5 year old started pre-k this year. We do NOT swear at home. He does NOT watch TV programs that have swears. His teacher explained to me that he seems to be VERY intrigued by a little boy named Chris, that misbehaves all the time. Everything Chris says and does, my boy says and does. The teacher keeps my boy, and Chris seperate during cl and lunch, but can't keep them seperate on the playground. Chris was sent home from school today, but my boy was not. The teacher said that my boy is LEARNING these behaviors and words, but certainly isn't bringing them on himself. This was basically our last warning about my son, and after this, he will be sent home as well, and possibly suspended. The teacher has called every day for 3 days now. The first day, i sent him to his room for an hour, and after, i talked to him about his wrong behavior. The second day, i sent him to his room, paddled him, AND his dad had a heated discussion with him. Today is the 3rd day, and he isn't yet home from school... what do I DO? and groundation in the room obviously aren't working....