Is it ODD or just a bratty child?
ODD isn't just being bratty. It's oppositional defiance disorder which is a mental health issue characterized by negative behavior. The behavior is not about being spiteful or willful, it's much more directly related to developmental delays, anxiety, an imbalance of chemicals in the brain or could be the result of trauma.
A bratty child will respond to correction but a child with ODD will not and can become more irritable and unmanageable without the proper intervention by teachers and parents.