Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

What: Shares of digital whiteboard maker SMART Technologies (NYSE: SMT) plunged 13.9% in early trading today.

So what: With no news coming out of SMART itself, many investors were left scratching their heads about what happened to their stock today. Our British sister site has the scoop: SMART rival Promethean World plunged 30% on an alarming earnings report filled with warning signs for the educational materials industry.

Now what: What's bad for the goose can also leave lasting damage to the gander. I'm surprised to see the panic contained to SMART and Promethean World while related stocks such as Corinthian Colleges (Nasdaq: COCO) and Apollo Group (Nasdaq: APOL) are actually trading up on this otherwise drab market day. SMART Technologies could be the canary in your personal coal mine, warning you to get out of educational stocks before it's (even more) too late.

Interested in more info on SMART Technologies? Add it to your watchlist.

Fool contributor Anders Bylund holds no position in any of the companies discussed here. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool is investors writing for investors.