The Blind Side is indeed a true story. It tells the inspiring tale of how a young man's life was transformed through the kindness and support of a family. Many of the events and characters are drawn from real life.
It is indeed a real story. The movie depicts events that actually happened to Michael Oher and his journey. However, some artistic liberties might have been taken for cinematic purposes.
In 'the blind side novel', social class is also a theme. It explores the differences between Michael's background of poverty and the more affluent world of the Tuohy family. And there's the theme of kindness. The kindness of the Tuohy family towards Michael is what drives the story forward and helps him grow.