The story in question is about a strange rock that is found then the person that touched it is taken over by an alien being. The town is eventually taken over but a young boy who is in love with his teacher somehow breaks the hold on her mind and eventually everyone is back to normal.
This is almost certainly Miss Atilla the Hun by Dean R. Koontz. I can't find any descriptions of the story online, but if you check out his anthology Strange Highways you should be able to confirm it.
I don't know about a short story which is what you have noted as the tag line. But, Robin Cook's 1997 novel "Invasion" has strange black rocks which take over people.
A brief synopsis can be found at Amazon. Warning, light spoiler alerts. http://www.amazon.com/Invasion-Robin-Cook/dp/0425219577
This was also subsequently made into a cheap T.V. moview. http://www.rottentomatoes.com/m/1117204-invasion/
Amazon.com Review Fans of Robin Cook's many thrillers will be happy to know another one is on the way. In this latest outing, Invasion, Cook envisions a contact with extraterrestials that is closer to Alien than to E.T.. A gigantic spaceship arrives in the stratosphere to dump some black disks onto Earth. Touch these things at your own risk, however; unsuspecting souls who handle the disks receive a sting, soon followed by flulike symptoms and ending in a kind of zombie assimilation into the alien consciousness. And make no mistake: these aliens are up to no good--we know this because the victims of the UFO-flu are soon transformed into hideous reptilian creatures. Apparently, one consequence of being trapped by the aliens is that victims lose all semblance of natural speech--most notably, contractions. The book abounds in dialogue such as, "You must flee, Cassy," and "The electrical grid has been interrupted. There will be no force counteracting the antigravity ..." Still, readers looking for a good beach or bathtub book will find Invasion is right on the money. --This text refers to an out of print or unavailable edition of this title.