Why do schools neglect the above average student?

School systems in our country spend way more money trying to bring below average students up to scratch than helping above average students achieve their full potential.  The No Child Left Behind act has worsened the situation, but it was a problem before that. There's something inherent in our minds that makes us think that these students can 'fend for themselves' because they are smart. But it in fact often leads to these students giving up on the education system, depriving the country of its future great minds. Also, from the inability to socialize with other people on their level, they often become antisocial and very lonely, leading to long term social problems.  It wouldn't take that much effort to make these kids feel at home, but we let them feel estranged from their peers and 'weird'.