Rejected kids are those with psychological and behavioral problems. They are aggressive, disruptive and poorly socialized. There is a strong likelihood that their behavior will continue through adulthood. The situation doesn't improve for them if they move to another school. Neglected kids, on the other hand, are ignored. They improve with intervention and a change in school placement.
Childhood and adolescence lasts about 18 years. Adulthood lasts about 70 more. You may not see the results of intervention until young adulthood, but keep at it. Don't lose hope. He'll be counting on your strength.
There is likely to be some type of underlying learning, language or visual processing, developmental, motor or psychological condition that's making her "look" different to other kids.
She may be "out of rhythm" in her responses, not pick up on social cues, not be competent in the classroom, or be able to follow the unwritten rules of the group's culture. Girls rely on language and social rules to establish relationships. The focus of their interactions is emotional. Boys, on the other hand, deal in "real life skills". The social "currency" of elementary boys is playground skills.
Make sure several observations are conducted. As a private practitioner for over 22 years, I know the freedom of being able to chase down any question I have about a child without worrying about a bureaucracy breathing down my neck. Your insurance may cover the cost of a private evaluation.
Find the answers. Perhaps she is anxious. Perhaps she's afraid she'll make a mistake and be humiliated. Perhaps he is so impulsive that he can't organize himself to play on a team. There are lots of "whats"; you need to find the "whys" underneath so an effective treatment plan can be implemented. Social skills programs such as Relationship Development Intervention, although targeted for those with autism, can teach parents way to help their children learn social skills. Michelle Garcia Winner offers resources to enhance social functioning, again, for those on the autistic spectrum, but the ideas are sound and can apply to a number of conditions.
I cannot express how much I learned and how much I enjoyed the book, Friendfluence, by Carlin Flora. An easy and entertaining read. You'll know why I want you to be bold about tackling the issues head on. It's really important.
That's it for now! Keep calm and carry on.