To the teacher and her pupils inside, everything in the classroom seems normal. But in a room behind a two-way mirror, equipped with listening devices, unseen observers can follow every detail of the lesson.
It may sound like a vision from a dystopian future, but it is a reality at the Nelson Tomlinson school in Cumbria, where staff have welcomed Big Brother watching them.
Nicknamed "the goldfish bowl" by teachers, the professional development room allows new and established teachers to improve their skills by watching others.
Janet Downes, the deputy head, teaches all her maths lessons in the room.
She accepts that some teachers may find it off-putting.
She said: "It's weird at first, not knowing whether or not you are being watched. I spent the first one or two lessons feeling quite anxious, although after a while you just don't think about it."
A fan of Big Brother, Channel 4's reality TV show, she said she could never understand how contestants could ignore the cameras, until she found herself in a similar position.
"Watching Big Brother on TV, you can't believe how stupid people can be even though they know there's a camera on them.
"But now I can see that people soon forget they're being watched and carry on being themselves."
She said teaching there since the beginning of term had already sharpened her practice. "I think the very fact that you are in a room and anybody can watch you at any time makes you think about your approach to teaching and take apart everything you do," she said.
It is believed to be the first time there has been such a facility in a classroom.
Peter Ireland, headteacher at the school, admitted that films probably lay behind the inspiration for the room. "I suppose I watch too many police dramas with line-up rooms," he said.
While lesson observation was already common at the school, the two-way mirror gives teachers a new perspective.
He said: "There are teachers who are every bit as skilled as someone on a football pitch. But the frustrating thing is, who gets to see it? If you watch Match of the Day and see Thierry Henry back-heeling, you will see it again and again.
"This is like being God. You get an overall view of what's going on. You can walk up one side of the room and see the pupils' faces, and walk down the other end to see the class from their perspective."
The scheme also allows teachers to see how pupils behave when they think they are not being watched.
Mr Ireland gives the example of one student who worked well when the teacher's attention was on him, but who drifted off-task whenever she turned to the others.
"I don't believe anybody knew just how that boy approached his lessons, because you can't have your eyes on 30 people at the same time," he said.
Pupils have also become comfortable with life under observation. Sometimes too comfortable, in the case of one student, who thought he would never be spotted hiding litter behind a radiator instead of taking it to the bin.
Mr Ireland said that experienced teachers could benefit just as much as new teachers by watching the techniques of the younger generation, who are sometimes more confident in group work.
He said: "I don't think there is anything more important than making sure the educational experience of my pupils is as good as it can be. But I'm not thinking of that in terms of getting new kit or forging new links with some posh outside body. It's about what goes on in the classroom."