Bumper stickers that announce 'My Child is an Honor Student at [XYZ] Elementary School'.
To me, this just seems to be the height of poor manners on so many levels.
Every time I see these stickers, I wonder 'Who exactly is this for?' The random guy behind you in traffic? Why the hell would he possibly care? At least with political bumper stickers, there's the justification of the theory, however misguided, that you might change someone's vote by implicit messaging (although to even state that idea out loud is to realise how ludicrous it is.) But here, it is impossible for the owner of the sticker to not realise that the world couldn't possibly care less.
And what message exactly are you trying to impart to John Q. Citizen, even supposing they do listen? There's two obvious implications of the sticker:
1. I am very proud of my child, whom I love dearly.
2. My child is very intelligent (and yours is not).
My responses to these would be:
1. No $#!7. That's so unusual for parents! Why not just get a sticker that says 'I love my children'? What's that, you say? Because it would sound ridiculous and obvious, like boasting that you always flush the toilet?
2. You're bragging about your child's grades? Do you realise how pathetic that sounds?
The second one, which I suspect is the point of the stickers, just seems so loathesomely gauche and shameless that it's hard to know where to begin. Suppose you're the type of person who loves to mention how much money they make, or how many women they've slept with, or what type of car they drive. You reach middle age, and every interesting thing you've done is getting further and further in the past. You need to justify your insecurities to a world that is passing you by. But sadly, it is getting harder and harder to find opportunities to just insert monologues about your accomplishments into conversation like a misguided V2 rocket aimed roughly at London. People are sick of the same stories about your long-ago glory days. How might you make up for the failed dreams of your youth?
Easy! Just get into vanglorious sloganeering about your child's accomplishments! Better yet, launder it all through the a cheap, see-through veneer of parental love and adulation. Nobody will ever spot the hidden subtext.
Putting a child's A+ test on the refrigerator is a sign of pride and love that the child will see.
Putting a crude boast about the same on your car is tacky and classless.