Yes, GROWTH is a Scrabble word!

Letter values in Scrabble US: G 2, R 1, O 1, W 4, T 1, H 4.

Is it a valid word?

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

(biology) the process of an individual organism growing organically; a purely biological unfolding of events involved in an organism changing gradually from a simple to a more complex level
a progression from simpler to more complex forms
a process of becoming larger or longer or more numerous or more important
vegetation that has grown
the gradual beginning or coming forth
(pathology) an abnormal proliferation of tissue (as in a tumor)
something grown or growing