Someone I have worked with recently shared that they were not sure why they should use a Neuropsychologist rather than someone else to diagnose their three year old child in an IEE. This had seemed obvious to me as someone who had a background in Clinical Psychology, but others don't necessarily understand the different classifications within the world of clinical psychology and why one title may be preferred over others in different situations.
A neuropsychologist is the elite in the world of educational testing. They have the most education, the most training,, and the most experience. All Neurop0sychologists will have a Bachelor's degree (either B.A. or B.S.). Many have a Masters degree (either M.A. or M.S.). They will have a doctoral degree (either Ph.D. or PsyD.), and they will have additional education in Neuropsychology. In addition they must have completed all training as a psychologist, and completed additional training in neuropsychology. After completing all of the above training and education, they also must past state tests that prove competency. A neuropsychologist is more than able to diagnose anyone with learning problems and in some ways may be 'overkill' for a younger or more disabled student, but their degree of fitness as an expert is pretty unimpeachable. The "neuro" part means they have studied the brain in more depth and they are able to administer tests that allow them to make more detailed assumptions about the brain.
A clinical psychologist is also someone that would make an excellent expert, although they have not spent the additional time studying neuropsychology. For many children this would be adequate, but districts are less likely to admit to the expertness of the Clinical psychologist than the Neuropsychologist. Keep in mind though, that districts rarely use Clinical psychologists to test the children in the district, so their "experts" in most cases are not as educated or trained as vigorously as most Clinical psychologists. Testing is the specialty of the Clinical psychologist, although their testing strength may not be in educational testing. Most often they test for psychological disorders. They will have had to complete state testing to ensure competency.
A school psychologist must have a Master's Degree and pass a state competency test. They are allowed only to practice in schools and their education focuses almost exclusively on learning to administer and evaluate educational tests. They have no continuing education requirements.
An LCSW or Licensed Clinical Social Worker is trained and licensed to be a counselor or therapist. This person would have an M.S.W. (Master's of Social Work). They must also complete hours of training and pass a state competency test. They have some training in administering and evaluating tests, but they have not specialized in educational testing and would not be considered an expert for the purposes of educational testing.
An MFT or Marriage and Family Therapist is very similar to an LCSW, except that their specialty is in relationships and they would receive either an M.A. or and M.S. in Clinical Psychology. They would also not have the necessary requirements to be considered an expert in educational testing.
A Psychiatrist is a medical doctor who specializes in administering medications for psychiatric conditions. Many children in special education may see a psychiatrist for medication management but they would not be considered experts in educational testing. They might be an excellent witness for some aspects of a case involving special education, but they would not be a expert in the area of testing.