This is a popular little song. Once you get to the “Monkey, monkey, monkey” bit at the end, one group continues singing (or playing) this as an ostinato while the others sing the song again.
I wrote this arrangement for my primary school recorder ensemble. The treble part is deliberately simple, as each year a few more children join the trebles and have to “convert” themselves from descant fingerings. I don’t teach them more than the very basics, but use ensemble music that lets them learn as they play along.
I also use this song with ukulele Wider Opportunities classes and clubs. It just about works with strumming a C chord on the first beat of each bar all the way through – there are a few dodgy disharmonies, but they don’t last long.