I really want to know the causes of a fever. how do children of the age of 12 get fevers at 38.9 degrees. how do you get rid of it?

Infection?: The main cause for fever is infection and it's important to identify the focus. Your child may need a thorough work up, including a physical exam and if indicated, lab tests. You get rid of the fever treating the cause.

Fever- see doc?: When to see a doctor when your child has a fever? Depends on the age and how the child is doing: http://www.parenting.com/health-guide/fever/when-call-doctor