Yes, PLATOON is a Scrabble word!

Letter values in Scrabble US: P 3, L 1, A 1, T 1, O 1, O 1, N 1.

Is it a valid word?

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

a military unit that is a subdivision of a company; usually has a headquarters and two or more squads; usually commanded by a lieutenant
a team of policemen working under the military platoon system
a group of persons who are engaged in a common activity