This is not an area I know all that much about, but from what I can gather, changes in definitions between the DSM-IV (Diagnostic and Statistical Manual of Mental Disorder--Version 4) and the DSM-V (Verstion 5) could have a significant impact on special education services.
According to this NPR story, since the mid-1990s the number of children diagnosed with bipolar disorder has increased by 4,000 percent!
In particular: have children been diagnosed with Childhood Bipolar Disorder when they actually have Temper Dysregulation Disorder?
If they used to be diagnosed as having Attention Deficit/Hyperactivity Disorder, and then with Bipolar Disorder, or Conduct Disorder--what difference will it make?
And most importantly, what are the implications of these decisions for medication, treatment, and special education services?