I don’t know when this was filmed, but judging by the clothing and hairstyles, it looked like it was around the 90’s or even the late 80’s. The principal said this was the fourth year the school had been sponsoring Gay Pride Day. So this has been going on for some time, assuming it is still in existance at this school. (I could only watch a few minutes of this, my blood pressure was about to hit new heights, so maybe they gave a date further into the video.)
It appears that it was filmed in 1996:
http://www.lifesitenews.com/news/archive/ldn/2007/apr/07042407