Your kid’s GPA will be evaluated in the context of their school. GPAs (unless re-calculated like the UCs) are not compared across different schools.
You kid should use your HS counselor to categorize schools, which will be based on all their stats, rigor, class rank. Fundamentally, if a school publishes an average GPA (admitted? Enrolled?) you can’t use that unless you know exactly how it’s calculated AND if that’s how admissions uses the GPA when making admission decisions.
I say this a lot on CC and elsewhere…but the CDS GPAs (a common source for enrolled average GPA) are calculated in many different ways and often in a manner that has nothing to do with how admissions evaluates GPAs.
FWIW, colleges make their own determination of the rigor of the classes. Many private schools often say something like classes at level XYZ are equivalent to honors, those at level ABC at the level of AP courses. In those cases, colleges use the school report, the course guide, and even sometimes procure a syllabus to do their own evaluation.
Your kid should follow what their counselor says regarding his classes and level, and how to enter them in the various application softwares that they may have to use. Good luck.