If he’s going for an ART degree then the portfolio will be most important. Grades may factor in for awarding scholarship money but not necessarily for admission to the school.
As for “reach, target” criteria–it depends on what type of art major your son wants to pursue. Illustration, computer animation, graphic arts, game art, motion design, design etc.
As an example RISD is very prestigious for illustration ( “reach”)
Ringling and CalArts are prestigious for animation with very competitive admissions (and so become “reaches” in terms of admission for THAT major). And at the same time getting into Ringling as an illustration major is more “target”. Depends on what your son wants to do.
As you look at schools look at student work. Some schools are more “experimental”, some very “traditional” etc. See if you like the quality of work–they vary greatly.