It’s a funny screencap because it doesn’t really capture the moment very well, but after Kurt reads out the line (beautifully):
Secretly, you’d love to know what it’s like, wouldn’t you? What it feels like for a girl.
Mr Schuester gives him this thoughtful, lingering look. What’s he thinking? Is he wondering how often Kurt has wondered what it feels like for a girl — as opposed to the “honorary girl” he says he is.
That’s what I’m thinking anyway.