I did not bother watching this as the topic title did not grab me at the time. However, my 70+ year old mom told about it yesterday ...
The little boy (3 years old?) appears to know all the words but started singing in the head banging section a bit too early, but no worries, his big sister helps him out.
Socialism - Let me tell you how it will be
There's one for you, nineteen for me
Should five per cent appear too small
Be thankful I don't take it all