Yes, PIZZAS is a Scrabble word!

Letter values in Scrabble US: P 3, I 1, Z 10, Z 10, A 1, S 1.

Is it a valid word?

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

Italian open pie made of thin bread dough spread with a spiced mixture of e.g. tomato sauce and cheese

Also: pizza pie.