Evals do have to go through the formal process, but if your speech therapist requests the eval (you still have to sign consent), it is probably more likely to go smoothly. I would discuss your concerns with her, and see whether she thinks she already has enough information from working with him on an ongoing basis to speak intelligently to his language processing skills, or if she agrees that sitting him for formal evaluation would help clarify his intervention and accommodation plans.

...pronounced like the long vowel and first letter of the alphabet...