Revealing mistake: When the children run along with the car waving, you can see a modern digi-watch on the wrists of one of the children, which was not produced during the 1970s.
Suggested correction: Without using slow motion of freeze-framing, how can you tell it's a digital watch? It certainly isn't clear on the DVD version.
Revealing mistake: When all of the students are jumping into the water, if you look in the background you can see a modern minibus vehicle, which existed only after the 1970s, which is when this movie is set.
Suggested correction: Unless you can state the manufacturer and model, how can you know it's not a bus from the era?