The parent-teacher conferences at Hogwarts have got to be wild. There’s a chance that parents of Hogwarts students see their children’s countless injuries at their magic school as harmless collateral damage. You can’t play Quidditch without falling off of your broom a couple of times. Wizards have pretty low standards for safety, considering Hogwarts is the safest place their children could be. If I were Hermione’s parents, I would have chewed Albus Dumbledore out for creating an environment where my daughter was frozen for weeks and missed that much school. 

I believe Dumbledore is why Hogwarts parents aren’t complaining as much as they should. They have so much trust in Dumbledore that they don’t want to fight him on how he runs his educational institution. Also, as we know from Harry’s many talks with the old wizard, Dumbledore is a master manipulator; his calm demeanor and countless platitudes about life will set anybody at ease.