Pink Floyd - Another Brick In The Wall 
Lifted from "Pink Floyd  The Wall" film, this video is actually comprised of two songs: "The  Happiest Days Of Our Lives" and "Another Brick In The Wall Pt. 2" This  video became the official video of "Another Brick In The Wall Pt. 2"  after the release of the film in 1982.
This single is by far Pink  Floyd's greatest ever mainstream success, instantly attaining classic  status, and is perhaps their most famous piece of work. 
ABINTW  Pt. 2 even became the protest song of a group of South African students  during the apartheid regime, the song was subsequently banned in South  Africa. 
The song itself is a protest against the rigidity of  British schools, and in particular, the boarding school system Waters  would have been part of as a young boy.
The poem read out by the schoolteacher is a direct reference to "Money"
The schoolteacher in this video was portrayed by the late, great, Scottish actor Alex McAvoy who passed away in June 2005.