Yes, QUARTS is a Scrabble word!

Letter values in Scrabble US: Q 10, U 1, A 1, R 1, T 1, S 1.

Is it a valid word?

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

a United States liquid unit equal to 32 fluid ounces; four quarts equal one gallon
a British imperial capacity measure (liquid or dry) equal to 2 pints or 1.136 liters
a United States dry unit equal to 2 pints or 67.2 cubic inches

Also: dry quart.