And just because some people will think I am confused about what song this is, the below is from the official description on the video.

Hallelujah sung by Kaylee Rogers and Killard House School Choir in 2016. Copyright 2016 Kaylee Rogers/Killard House School Kaylee, a student at Killard House Special School in Northern Ireland, who suffers from autism and ADHD; stunned the online world with a choir rendition of Leonard Cohen’s “Hallelujah”.

Why this is song that is so different from what most people think of as Hallelujah is because Leonard Cohen wrote a lot of lines to “Hallelujah” and different people including himself use different parts of it to make songs out of.