Check out WRITESLAW, PACER and ARC websites. Each of these (in my humble opinion pacer is the easiest and most parent friendly for basic IEP and assessment procedures for a newbie, writeslaw has tons of info about the laws and rights of your child etc.)
If this school is a public school they are obligated to provide special education services but of course that doesn't mean they are a good match. To decide that before an evaluation is done and before any interventions have been tried, that is suspicious to me (of course just my opinion, and not that they are evil but just maybe not equipt and not very aware of what a child like yours really needs) and I am afraid of their results being skewed not on purpose, just that they may be looking to support their position. Now standardized tests are harder to skew unless it is teacher rating scales etc. It is important they have you and the teachers fill them out to compare results. I have never had it done any other way either for my son or for any evaluation I have been a part of. In this case I would say you for sure should look for a private evaluation as well. And if you do not agree with the results of the school's evaluation, you have the right for a second evaluation thru a private party at their cost. You may have to choose from those they contract with, but it is a right you have.
A basic premise of IDEA is that the child is to be educated in the least restrictive environment. You will hear LRE alot. The way that is interpreted by most states and school districts is that the child will be educated with non disabled peers to the maximum extent possible using modifications and supports right in the classroom and school. (for my son LRE is to not be with non disabled peers all of the time but only some of the time, so obviously it is different but you typically start with peers THEN if supports dont work go to more seclusive, first a resource room, then a class, and maybe a separate setting). It is very hard with charter schools and magnet schools, sometimes they just dont have the special needs kids large enough numbers to justify having full time Special Education. staff there, so even if it is a good school...you will have to decide if it is worth being with people who dont seem to eager to have your child or to make a really sincere try at educating him in that setting, as well as not having the staff who would really understand his needs and could help advocate for him in that setting. (IF that is the case there) Many typical schools have smaller gifted and talented class programs and also have Special Education staff so your child could have the benefits of both. It is worth checking out all of the schools and while they may not advertise that they are geared specifically for GT programming, they may still have it. They typically are very careful about recommendations because if they are saying they dont have the resources to educate difficult child in their district, and are saying you should go there they would have to pay...but I doubt that is what they were saying. Probably just a suggestion. The law does not require the best placement, simply a placement that provides adequate educational services...sigh.
If you have an ARC chapter near you they have free educational advocates. Check your state education dept. website and see if they have a page to refer parents for educational advocates. Ask parents . An educational advocate helps you navigate the legal assessment/IEP process to prevent conflicts or to help when there are conflicts and issues. An ed. consultant is usually someone who works more on just developing the plan and walking you through a non-conflict process (now of course there are individuals who vary just that is broad typical description). Usually a lawyer isn't needed until there really is a conflict that you are not able to resolve using the due process procedures built into the system. There is a free mediation level of solving things that often does very well. Now, if they seem "off" from the beginning, and you have the means, just knowing you have a lawyer may just keep them in line and you might not even actually have to use them. I tend to go into it thinking people are sincere in doing their best, but that doesn't mean they are doing THE best job. So as you go through check in often and see if anyone here has had a similar experience. One thing I think we all would say to do, even if you are new to this process... trust your gut. I only really feel guilty about things going wrong when my gut had told me so and I didn't follow thru.