The category of emotional and behavioral disorders (ebd) is very broad. Almost everyone, at some point in their lives, could be classified as having an emotional and/or behavioral disorder. However, in terms of how the federal government defines emotional and behavioral disorders for children, there are more specific guidelines.
For purposes of consideration for receiving special services, a child must be classified as "seriously emotionally disturbed" or SED. The way SED is defined by the federal government is vague and can be interpreted in different ways. (see section on laws for more info). However, most states and school districts interpret the law as narrowly as possible. This results in far fewer children in the category being served (for special education) than the actual prevalance of ebd in the population suggests should be served.
To further complicate things, emotional and behavioral disorders can be defined in different ways. The psychological and medical community frequently use the DSM-IV to classify ebd. However, this system is rarely used in the education community. Educators frequently classify students based on functional behaviors and interventions. One such classification system (Quay and Peterson, 1987) categorizes students into six categories: conduct disorder, socialized aggression, attention problems-immaturity, anxiety/withdrawal, psychotic behavior, and motor excess. The more I read about them, the more I'm not fond of any of these classification systems, and think that "categorizing" kids in these ways is not useful. Rather, I think it's better to evaluate an individual kid and treat them with mental health counseling based on his/her unique problems. Unfortunately, for purposes of receiving special education assistance or medical care (insurance), the trend is to assign everyone with some sort of code or label.
First, get a good evaluation. This should be done by a school psychologist or mental health professional (counselor, psychologist, or psychiatrist). This should NOT be done by a family physician or educator, they are not qualified to make diagnosis. A good evaluation should include interviews with the student, parent, and teachers (and others involved in the students life), and testing. Ideally, this assessment process should occur over more than one time interval...ie, the entire assessment should follow the child's behavior over time, not just a one-hour thing.
Second, work as a team. Parents, students, teachers, counselors, and others should work together to help the student. A treatment plan should be devised and mutually approved of. If teachers and parents disagree, the child will probably end up not doing well.
Third, periodically re-evaluate the child. Is progress being made? If not, adjust the treatment plan.
Fourth, don't sweat it. These days there is little stigma attached to special education, or mental illness, or even to taking medications. Everyone has problems, and most people are understanding and want to work together to help.