Yes, POSITIVES is a Scrabble word!

Letter values in Scrabble US: P 3, O 1, S 1, I 1, T 1, I 1, V 4, E 1, S 1.

Is it a valid word?

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

the primary form of an adjective or adverb; denotes a quality without qualification, comparison, or relation to increase or diminution
a film showing a photographic image whose tones correspond to those of the original subject

Also: positive degree.