When talking about ADHD medications what are the pro/con of medicating the day of the test versus not?

Not medicating-Will make a "controllable" diagnosis show up and since school districts now have to address the diagnosis even if mitigating measures are in place that diminishes the effect of the disability, it can be addressed as there may be days when medication is forgotten, etc.  42 U.S.C. § 12102(4)(E)(i).

Medicating-The effects of a primary known disability that medication mitigates could bring an unknown secondary disability to the forefront that has been masked

Is there a firm rule on when to medicate and when not to? Does it matter only on IQ testing? Academic testing? What about auditory screens? 

There is one research study I found that says Ritalin, for example, had a significant effect on the Auditory Continuous Performance Test (ACPT), but should parents medicate kids when going in for a central auditory screen?  Audiologist said either was fine, but is it? 

I'd recommend checking with your doctor for medication questions. 

My question would be, on a regular day, is the ADHD medication part of his normal routine?  From the school nursing standpoint, I would not alter anything that you do on a normal day that represents the typical academic achievement. Yes, you should be consulting with the treating practitioner, and yes, 504 services are there regardless of medications that mitigate symptoms. Is the testing for IEP/IDEA services? There shouldn't be any testing required for 504, and in my overall suggestion is to have available at school, a just in case bottle of the daily medication - no more than 2 or 3, that are there specifically for those days that are in the toilet before they even get started! That can be written into a 504 with specific qualifying administration instructions. Just as I would not recommend testing on a child with an illness or fever, I wouldn't for a child who is not following his/her normal daily routines, including daily medications.