IT may carry an echo of TV's Big Brother, but this could be the future of maths teaching in Britain.
As Matthew Read fires off questions, class 10T2 attempts to master geometrical reflection. But Mr Read is nowhere to be seen.
The advanced skills teacher's voice is booming out from three speakers as, 400 yards away in another classroom, he simultaneously teaches a second group of 14 and 15-year-olds.
Mr Read works at Toll Bar business and enterprise college in Grimsby, Lincolnshire, one of the first in the country to set up sound and video links allowing staff to teach up to 90 pupils at a time.
For some, the arrangement underlines National Union of Teachers' concerns about rising class sizes. But the 2,000-pupil comprehensive insists the move does not simply tackle teacher shortages, but allows pupils, other teachers and struggling schools to benefit from expert teaching.
Cameras in both classrooms mean class 10T2 can watch either Mr Read on a big screen at the front, or on the electronic whiteboard on which he works during the 50-minute lesson. At all times, they hear his voice.
Another maths teacher, Janice Hornby, sits in with class 10T2. When Mr Read wants a question answered, he hands a microphone to a pupil or gets Ms Hornby, in the other class, to do the same.
Mr Read has been delivering these lessons since last term and they are soon to be expanded to science and information and communications technology.
Principal David Hampson said the school did not have any vacancies in maths or science. But the scheme, which requires only one qualified teacher, would soon be used in ICT because Toll Bar would not be able to replace the head of that department until September.
Toll Bar is offering free linked lessons to two local secondaries where headteachers have recruitment difficulties. The scheme was developed as a pilot by the local authority, which wants its secondary teachers to teach pupils in "feeder" primaries, and vice versa. It believes three classes could be hooked up at once.
Already Toll Bar is talking of offering further maths A-level master classes to students from across the country.
So does the technology, which costs pound;12,000, work? There were few glitches when The TES visited the school: Mr Read was impressive and the 55 Year 10 students attentive and well-behaved.
There will be reservations about the level of attention any child gets in a "class" this size. But given the national shortage of maths and science teachers and that schools are keen to make teaching expertise go further, it is hard not to see arrangements like this taking off.