Rachel K. is right- medical diagnosis does NOT automatically qualify you for an IEP. Having him tested outside of school and having the results sent to the school also will not automatically qualify him for an IEP or speech services. It's just not that simple!
If there was an IEP in place already, then yes, they have to follow it. If speech is not on the IEP, then no, he does not get the service without an evaluation and a determination of qualification for these services.
If speech WAS on the IEP, they cannot simply dismiss him without conducting a complete re-evaluation and justifying the dismissal.
Have a chat with the SP at school and read your IEP. Good luck!