And where he already has a documented Dx for TS, and school eval reports (the BASC) indicative of impacts from the disability, a 504 plan ought to be a shoo-in, if you don't already have one in place.
I'd echo the IEP eligibility eval request. Put it in writing, and the school must respond to you within 10 school days, with either a refusal to act (must explain why), or a request for consent to evaluate. Once you sign consent, the eval, meeting, and IEP development process must be completed within 60 calendar days, not including summer vacation:
http://odr-pa.org/parents/parent-resource-library/timelines/So if you start the process now, the deadline will fall in the first month of the new school year.
If you prefer to have the PCP-referred neuropsych do the eval, then you might consider notifying the school that he has an upcoming eval, and then (most likely over the summer), putting the request for IEP eligibility determination, but entering the outside eval report into the process, so the school doesn't unnecessarily duplicate assessments. They may just accept the report, or supplement with a smaller selection (probably achievement testing), in which case, there is the potential for an expedited meeting in September.
Note that PA requires that an ID'd GT student must have his gifted needs addressed in the same IEP that addresses his other exceptionality(ies).
