Yes, KOALAS is a Scrabble word!

Letter values in Scrabble US: K 5, O 1, A 1, L 1, A 1, S 1.

Is it a valid word?

KOALAS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

sluggish tailless Australian arboreal marsupial with grey furry ears and coat; feeds on eucalyptus leaves and bark

Also: koala bear, kangaroo bear, native bear, phascolarctos cinereus.