In the strip, not so much the movies and specials, Peppermint Patty, Marcie, Franklin, and I suppose Roy all go to a different school than the rest of the gang. So Charlie Brown may not know what his dog is up to.
For me the silliest arcs are Sally’s “conversations” with the school building (and other strips like it). That requires more suspension of disbelief for me than any other storylines in the strip. But to each his own, of course.
Build it and he will come. Actually, he’ll probably come anyway.