College is the last thing you would consider as a factor. The im

Unless your kid would attend Chinese university, going back to Shanghai hoping to get in better American school is not sensible. Going to Shanghai wont' give you more competitive edge for better American college, if not less.

This kind of dramtic change would have huge impact on your kid, especially at that age (teenager).  Depending on how kids deal with it, the results could be very good, or very bad. 

My son went with me to China in the summer after grade 4, and forunately it turned out to be very positive.  He was shocked initially, but emerged as a "hot shot" in his school.  One of my friends wasn't so lucky, and they had to return back the States only 2 years later because of his son's inept coping with the changes.

We decided to come back to States when he was about to attend high school, and his international experience has always been an asset, not so much for the resume on college application, but more as a person.