Not a kid anymore

My 5th & 6th graders all have email accounts through the school. We use them frequently for school related things but the students also send personal emails back and forth. As domain administrator over them I can view the emails they send back and forth (just to make sure nothing inappropriate is going on). Well, just to keep them in check, I sometimes make reference to an email that was sent from one to another that I clearly was not part of. Two of the girls in my class send emails back and forth that seem to make no sense and I mentioned this to them back a while ago. Today, out of the blue, I received this email from one of them:

Subject: My gmails

"Ms. Sjoberg, I think that why you don't understand some of our emails is because you aren't a kid anymore. You are past the age of 18 and you are past college. If you think I am wrong then just say so, but that's what I think."