You can go for a recertification as a school psychologist. The University of Northern Colorado has a program. Not sure of other schools, but I am sure they are out there.
For UNC, you must be a licensed psychologist or be eligible to become a licensed psychology (i.e., graduated from a Ph.D. or Psy.D. program, and fulfilled the appropriate internships).
Their recertification program includes 4 courses, 2 of which are online, and the other 2 are on weekends. In addition, you must complete a 1200 hour internship. If you have an appropriate amount of compatible hours with your Psy.D. practicum/internship, these hours can be reduced to 600.
So basically, for an additional year and nominal financial investment, you could be a licensed psychologist and a licensed school psychologist. I understand the desire to do it this way, as it maximizes your earning potential as well as allows you to work in a multitude of settings.