Looks like he meant an S there, not an R. I would know, because as I said it's almost like my writing. 
Definitely an S, his R looks different. And the S is similar to those in the words is, has, does and muscles. Especially the S in "is" of the first sentence is identical to the last letter of "boneS". I'm beginning to think less funny thoughts about a teacher thinking about a boneR among ten year old kids...
