It depends, quite a bit, on age and culture.
A few years back I had a class of 11 & 12 year olds who loved Baby Metal and they learnt their song about bullying.
A couple of years back I had a class who wrote a collab rap about standing up to bullies.
My last full time teaching year the class wrote their own graduation song - a rocker called I'm A Teenage Zombie..as they were moving from 12 to 13 and primary to high school.
Songs like I'm a Little Aeroplane go down well with 6-8 and they'll hold on to it through to their teens.
What matters is a simple, short melody, strong rhythm and a narrative that is either easy to relate to or absolutely silly.
That said repetition is very important as is humor.

Cheers
rayc
"What's so funny about peace, love & understanding?" - N.Lowe