The following statement is via Reddit:
Hi, Valedictorian at Basha High School, a.k.a the school seen in the video above, here, created a Reddit account just to explain to you guys what's going on because Twitter is a firestorm and Reddit is usually better at that sort of thing.
This is known as the Paper drop, a very long time school tradition at Basha where all the seniors gather in the F Building stairwell after the second bell of C lunch on the last day of school and toss every paper, yes every paper, that they have saved up over 4 years of attending the school. Each year students bring trash bags full of paper to the school and dump them all at once. The "waterfall" you see in the video was only a little of a probably 5-10 minute drop of paper.
Afterwards, seniors slide down the stairs and go outside to where they take pictures, say goodbye to teachers, and say goodbye to the school for one last time as graduation is done at Arizona State University. While the seniors are reminiscing, underclassmen from across the school, as well as a teacher that brings a leafblower every year, gather the papers up into trashbags to be RECYCLED while the janitors talk and watch along with everyone else.
Basha High School is a fantastic place that's had its ups and downs, but this one event brings together everyone from geek to jock into one, single, Basha Bear student body.
Thanks and upvote this to show people what's going on.