Anyone can fall behind. There can be any number of reasons why. The behind student today might be the ahead student tomorrow if there are resources that enable that student to catch up.
But if we devote most of our resources only to the ahead it's like saying "screw" anyone who is unlucky or ever had a bad day. That's what we call... evil.
In elementary school my teacher thought I was terribly behind in reading and should be put in special education. In High School I graduated as valedictorian. Maybe you think they should have taken the resources away from me and given it to the kids who could already read well.