Green’s Dictionary of Slang

(Aus.) kindergarten.

1962		R. Campbell Daddy, Are You Married? 83: ‘She’s still in the bubs. The bubs are too little for me now,’ said Little Nell complacently.
1988		F. Richmond Remembrance 64: Some rows of spidery pot hooks from my brother who’s in the Bubs at school [GAW4].