I have discovered the answer!
I was reading Dawn and the Big Sleepover and found this:
Ms Besser said to Dawn: "Do me a favour. Would you mind staying exactly the same age for a few years until I have a child old enough to be bay-sat for."
!!!
Well done Ms Besser. If you ever get sick of Stoneybrook Elementary, there might be a job available for you at Hogwarts.
Ms Besser said to Dawn: "Do me a favour. Would you mind staying exactly the same age for a few years until I have a child old enough to be bay-sat for."
!!!
Well done Ms Besser. If you ever get sick of Stoneybrook Elementary, there might be a job available for you at Hogwarts.