This is definitely not USSR championships. The person who posted this on another forum said that he found this film near a control line site in Bogorodsk, a town about 3 hrs east of Moscow, in 1974. He was not sure which contest was depicted on it. However it is clear that the participants are pretty young and do not have all the 'pro' level skills, so most likely high school students.
Pretty neat piece of history, however. That was back when racing planes looked like planes and not pancakes married to an eggplant, and a race could be won with a decent store-bought engine rather than a $1500 hand-fitted piece of machining art. And we were young...