ALthough I do completely agree that a twelve year old could be a protaginist, I would like to argue in "The Sixth sense" Haley joel osment was not the protaganist, but bruce willis was.  Same thing for the exorcist, the little girl wasnt the protaganist, but the preist.

Not disagreeing with the actual argument at hand, 12 year olds totally work and many of the examples put out there have been great, just in my opinion the sixth sense and the exorcist arent.  I was actually thinking the shining, that kid is younger than 12 and I would consider him the protaganist.