If middle school students started to act up or act like little kids, what do you think about this situation?

Today at work, a 2nd grade teacher told them off saying, "One thing I don't understand is how can 7 and 8 grade students like you let 8-9 year old kids do you like that or tell you what to do when you're suppose to be acting like middle schoolers? I don't get it at all." Their teacher said, "They have NOT been acting like middle school students recently. Disappointed especially to the ones that are going to high school next year." Ouch harsh. What do you think?