While my son already had an IEP for developmental delay, the school district paid for an outside neuropsych evaluation. We did not now what had happened to him at the time but the school was not agreeing with the labels given to him by other outside evaluators - bipolar, autistic, schizophrenic. My ds was/still is/in a full exacerbation for quite a long time and his symptoms are constantly changing. The testing did help to expose some teaching strategies that were beneficial if they could get him to attend. Unlike the others here, my ds was on grade level at the end of kindergarten and his symptoms were so debilitating that he could not function to learn. We are two years later (2nd grade)with a child at the end of kindergarten level.
Being a previous reading specialist and teacher, I know that an outside evaluation will be helpful in obtaining aid for your son. The school district does not like outside evaluations. They like to test their own. First, I recommend writing a letter to the principal indicating your concerns and ask for a team meeting/case study. By law the district must give you a meeting because a parent requested it. This doesn't mean aid will be given but it definitely is a starting point to air your concerns with the teacher, administrator, psychologist, social worker, etc. I hope this is helpful information for you.