But Thompson has also faced threats and vandalism from others. Thompson's also taken criticism online after a picture of the sign when viral on Facebook for calling out other parents in her neighborhood.
"It hurts, because I'm trying to do something for this community. No one does. No one cares. I do. What was one of their kids?" said Thompson.
Even though the sign says it's a promise, not a threat, neighbors say some are taking it that way and that's the wrong way to go about it.
"It just seems to aggravate people, so they stop here and peel out and try to antagonize, rather than cooperate with the sign. So it's not really working," said Barb Allow, neighbor.
Still, Thompson says she's not giving up.
"If I don't continue to make an awareness of it, who's going to?" said Thompson.
Green Bay Police say the only issue with the sign is the top part that looks too much like an actual speed limit sign, and is too close to the road. The rest, they say, is freedom of speech.
Jenny tells us she will comply with whatever the police ask her to do.
TODAY'S TMJ4 sister station, NBC26 asked police for more details on the accident Thompson told us about that lead to the sign and they say they couldn't find any record of it.