You are in the classic catch 22. As long as there is no educational need for special education, even a formal diagnosis is not going to help him. IDEA is very clear, to qualify for special education the child has to meet a two pronged test: A qualifying diagnosis (dysgraphia is NOT one of them btw) and the child must need special education. Your son will not meet either standard, although, he may meet the standard for a learning disability in Written Expression. My first question is, has he taken the MO state assessment for writing yet? Yo do not say what grade he is in, but in most states, children do not take the state assessment for writing until the end of the 4th grade. If he is in the 4th grade, and has yet to take this test, you may find that his score gives you the evidence to prove need.
I can tell you what assessements you need. You should get an IQ test, a WISC or a Woodcock Cognative, and you need an acheivement test, the Weschelser Test of Acheivement, or the Woodcock Johnson test of acheivement. Both should be full assessments, not "screens" and for the achievment test, you want a full battery of subtests and you need the full written expression score. You should specifically request that every sub test be given in the area of writing and written expression so that every composite score can be expressed in this area. Especially if you are sucessful in getting school testing done, they will not do all the subtests to avoid actually testing him in any area that will show need. The old way to show a learning disablity is to show that the child has a difference of at least two standard deviations between their full scale IQ and their score in the area of disablity (in this case, written expression.) The new gold standard is something called response to intervention, which I will talk about in just a sec.
This descrepancy modle would probably reflect a learning disablity in your son's case, so I would predict that you can meet the first prong of the test will minimal testing (which you can purchase yourself, kind of alacarte from a neuropsycholgist.) It will not show need, need is going to be based on curiculum based assessment, grades, and his score on that state assessment. In some very rare cases, psychological decompensation due to a learning disablity can cause need, but this is a hard argument.
Another suggestion to you is to see an Occupational therapist, they may be able to help him with some therapy, if some of his issue is fine motor, visual motor, or visual perceptual. Some of this therapy may be covered by your insurance. Also, a trip to a developmental optomitrist (OT's can refer you) would be a good idea to rule out an occular motor issue that could respond to corrective lenses, which may also be covered by insurance. Ruling it out is a neccessity.
As for the RTI, or response to intervention, you may be able to argue that he needs some intervention without a diagnosis. RTI is supposed to be implemented for all children who show need (without any diagnostics) hoping to remediate issues and prevent children from needing evaluation and lowering the numbers of children who eventually develop and are diagnosed with a learning disablity. It kind of sounds like this is not going on at your school, but sometimes, if you appear educated about these things, they will magically start to happen. You can log on to www.wrightslaw.com and read about RTI, see if you can get anything going without a diagnosis.
You can get the full diagnosis of dysgraphia from a developmental pediatrician. Explore your insurance benefits on this too, you may be surprised about the coverage. You can find developmental pediatricians at every children's hospital, but getting it can take 6 months or more. Just remember, even if you get this diagnosis, you need the full evaluation with all the subtests on the Weschesler or the Woodcock Johnson to get the school to recognize a learning disablity in written expression. Spell it out, be sure you get it, you have to ask, and double check.
For all your private evaluations, if you find that later you get the school to evaluate, and they should have evaluated, you can ask for the school to reimburse you for your cost; however, you must be able to prove that you requested that they evaluate your son prior to you spending that money. The only way you can prove that is if you have a document to proove it. If all your requests have been verbal, put pen to paper and write a request to the director of special education requesting an evaluation for your son and something called "Prior Written Notice" of their reusual if they refuse that lists all the tests, assessments, and measurements that they used to determine why they denied your request. Every time, from now forward, that you have a conversation with anyone at school about this issue, send a confirmation email that day that summerizes everything you say and they say, and at the end, say "if you do not send me a written correction within ten school days I will assume that I have summerized our conversation accurately." If it did not happen in writing, it never happend.
Good luck, if I can answer any more questions, let me know, this is what I do!
M.