Gifted 11-year old unmotivated/bad grades of late?

Just because you know his friends doesn't mean he isn't being bullied. That was my first thought. There is obviously something going o.you are unaware of. I would contact the teachers individually and set up a conference and see if they have noticed anything. I would also contact the school counselor and see if they know something, or have any ideas. He could just be bored.