I would not let him play with it. I do not ever leave string or rope of any kind out for my cat due to
-It's a choking hazard in the way that they can either get it stuck in their mouth and choke, or get it tangled around their neck.
-If the rope is swallowed or strands of the rope fibers are swallowed, you are looking at a costly surgery.
I've pulled my fair share of rope and ribbons out of animals butts. It is not pleasant.
The only type of "string" I let my kitties play with are pet-safe ones that come on cat toys.. they are soft and don't fray so they don't pose a choking hazard. I have never had any issues with those types of rope.
My cat is smarter than your honor student.
Stop Dog Fighting ~ Neuter Mike Vick!
~ RIP Timmy ~ May 2009 - November 6th 2009