A supplier who provided the school with an electronic whiteboard confirmed its position in London in 2010.
Promethean World shares, which were recently listed at 200 p, fell 19 p yesterday to 96 p.
It has never been cheaper than it is now to admit that tighter education spending in the United States has hindered sales from July to September and may do so for the rest of the year.
Although Promethean, which accounts for 2 out of all its sales, has highlighted its confidence in its ability to achieve the city's profit target this year, brokers have still reached their red pen.