Another idea: Teenagers are told to stop growing, so the yardstick (which is a measuring tool that is fixed) might say, "I can’t stop being a yardstick!" or "You’re always measuring me!" Maybe the punchline is "Stop expecting me to be perfect, just accept my flaws!" (since a yardstick has marks for measurements, maybe flaws as in the lines or something).
Alternatively, considering "yard" and "stick," maybe a play on words like "you're the stick in the mud," a common phrase. So the yardstick could be saying, "Why are you both the measure of how bad things are?" or "I’m trying to bend, but you won’t let me!" Another idea: Teenagers are told to stop growing,
Wait, I think there's a common joke where the yardstick says, "Stop measuring me by your standards. I can't grow if you keep comparing me to others!" or something along those lines. But maybe more punny. Let me think: "I can't stop growing inch by inch!" or "You're the measure of all things negative in my life!" I can't grow if you keep comparing me to others
But maybe the actual answer is a pun, like "I'm at the end of my string!" (since strings can measure things) but modified. Or "You can’t always be on my side (edge)!" (yardstick has straight edges). Or "You can’t always be on my side (edge)
Another angle: The yardstick is a teenager, so maybe it's saying "You don't measure up!" But that's the parents being told not to measure up, which is a bit different.
First, I should figure out the joke itself. The title suggests a riddle or a play on words. The yardstick is a measuring tool, right? A teenage yardstick would mean it's personified, so the joke is probably about the yardstick's issues with being measured or not being flexible in size. Since it's talking to its parents, maybe the parents are trying to measure something, and the yardstick is being rebellious?