Blackcat I suggest that if possible you change the title of this thread so that it reflects that you are asking about speech issues. There are people on this board with a ton of experience getting speech services both inside and outside school but they may not read and respond if they don't realize that is what is being discussed on this particular thread.
Our IEE was in response to school SLP's eval that was done as part of DD's triennial. If speech services are included in your DS's IEP then I assume they WILL be doing this eval. You then reject that eval and request IEE by a provider of your choosing, ie the apraxia SLP your insurance doesn't cover. I knew in my mom gut that school SLP was bad and the eval she did was worthless. I did the full eval covered by insurance for my own peace of mind and so I would know what to push for as part of the IEE. It also gave the "protector" something to use as she had to know the school SLP's eval was garbage but her hands were tied.
So no don't go back to the hospital clinic. You don't want a student or resident doing this eval. I went to the state flagship university with an excellent speech and hearing clinic and had a faculty member do the eval while 2 grad students and I observed through one way glass. As someone told me students are being trained to look for horses not zebras but our kids ARE zebras. We need someone who already knows all the rules and can recognize when a kid is outside the lines not who is in the process of being trained what the rules and lines are. In so many areas my DD would make a student or a resident's head explode. When top people who have been seeing the most unusual of cases for their decades long careers have never seen anyone like DD how could a student or early career person possibly know what to make of her? Choose the most experienced person you can find and talk to them in advance to be sure they understand his issues.
The oral motor guru trained the new school SLP to work with DD. The protector SLP also attended the training session so that she will be able to train the next person if this one moves on. Old school SLP never would have agreed to attend this training. She was very happy with her limited knowledge set being applied in a way she was comfortable. Unusual situations require creative problem solving. This is where an outside advocate or consultant can be very helpful. Mine has been worth his weight in gold. Yes I pay him and now I can basically do this stuff on my own but his skill at getting the district to provide services and pay for evals has been priceless. That's how I would be looking to spend money now if I were in your shoes.
