Proud parent... period! The saying is nice. Much better than the Proud Parent of an Honor Student at Blahblah Middle School, Proud Parent of a C+ or Higher Student (well, except for math. But every kid sucks at math), Proud Parent of a Dog, etc. stickers.
But... huh.... something's not right.
Shouldn't it be "Proud Parent... period."? I mean, I know they're super excited about how proud they are, but if you're actually writing that the sentence should end with a period, you should end it with a period. Or else it should say "Proud Parent... exclamation point!" But that's a bit wordy, dontcha think?
Maybe their kid isn't doing so hot in grammar either. That's why he/she is not an honor student. That's why they can't proudly display that "Proud Parent of an Honors Student" sticker on their car.