School Zone Graffiti? Or Is There Another Answer?

Have you ever gone through a school zone and seen some funny lines on the ground? Were the road crews bored and just plating around or is there a reason for what they did?

I recently wrote a blog about a school in Oklahoma that found drawings on a chalk board from 1917. You can read it here if you missed it. While I was going through Google street view for an image i noticed there were squiggly lines painted on the road around the school but only in the lanes furthest from the school.  So what are they for? are they to mark that its a school zone? if so, why only on one side of the road? Do they indicate that there are no left turns?

 I'm puzzled by this and want to know, have you seen anything like this anywhere else? If you have, share a picture and let me know what you have found out about it.