There is not a psycho educational test that can definitively rule in or out ADHD, but there are often certain red flags and patterns that diagnosticians look for that may lead to an ADHD diagnosis.
One red flag is a trend of higher scores on un-timed tests relative to timed tests. On the WISC, folks with ADHD often have lower PSI, or WMI or both relative to VCI and PRI. Evaluators often administer tests in the area of executive functioning, and often people with ADHD score lower relative to their thinking skills or academic skills in one or more areas of EF.
But, just because one scores very well on standardized testing, one could not rule in or out ADHD. ADHD is a clinical diagnosis, and the doctor would most likely consider data beyond testing. In fact, if someone does very well on academic standardized testing, but bombs in the classroom - I would want to understand the barrier to classroom performance. Things like organization, ability to stay on task, planning, sustained attention, ability to switch tasks, ability to deal with the big picture and details in a balanced way etc are needed for good grades and classroom performance. Often times ADHD presents challenges in this area. Thus you have what looks like an under-performer. But really, something else could be going on such as ADHD.
