Every show, even a satire like Suburgatory, needs reasonable characters, people who have brains and are somewhere in the ballpark of real life people. "Charity Case" goes waaaaaaay overboard in making the supporting characters dumb, and gets lame quick. The school is clueless and ignorant to no end while Tessa, clearly the only sane person, tries to teach them something. The episode is filled with these silly, stupid moments, topped off with Tessa sort of understanding where they are coming from when she doesn't want to stuff people give her.
Plenty of sitcoms feature exaggerated characters and worlds, but the good ones manage to dial it back just a bit to let the human elements shine through, making one dimensional characters more than they are. Suburgatory, however, still has a long ways to go if "Charity Case" is not an aberration.