the majority wouldn't stereotype the minority.
Introverts haven't always "checked out." We aren't always isolated by bad circumstances, silently plotting revenge on the world.
Most of us just have a very rich inner life, are immersed in our thoughts, and aren't that interested in the surface activity that comprises most of human interaction.
No "back of the class kid" has ever gone unnoticed, or ignored, by me.
I wish I could get more middle school students to spend more time thinking, more time reflecting. The reality is that the vast majority are really uncomfortable with quiet, and really uncomfortable with just themselves.
Put that quiet kid in a very small group, no more than 3, and make sure everyone in the group has to add to a discussion. Then sit back and listen to what she has to say. Do that regularly, and pretty soon, everyone in the class will want the back of the class kid in their small group, because they know their group will have something worthy and interesting to report out to the larger group.