It shows a photo. And used that as the basis for the claim. But the article I linked which is long and gives a lot of the story of the school states a number of times it was created in the 1980s. I don’t know if it was repurposed from an old closed building or school or what.

Whether it was there first or not seems irrelevant anyway. If we care about the health of the students the whole school should be moved (unless you think we can move the freeway instead).