Hi
I understand that your child speech & language skills isn't appropriate to age. There could be delay in speech and language development. Delay could be due to lack of stimulation of language & not having favorable learning environment or due to any other developmental disorder. Her aggressive behavior could be due to various behavioral issues developed due to delayed language development.
Next Steps
You should approach a Speech Language Pathologist immediately. If needed the Speech Pathologist may refer you to Clinical Psychologist for behavior modification, you might need to learn to modify her behavior by making changes in her environment. She might learn to mingle with other in school but that's not a solutions.
Modify her environment by providing her lot of input in language. E.g. Start activities like describing of various things in the environment, Story Telling, increase the duration of your interaction with her, once you start providing adequate input except more from the child. Spend more time taking to the child.
Hope this answers your query!
Health Tips
As age increases ability to acquire language decreases. If the delay persist there might be difficulty in learning academic skills.