Yes, PLACEBOS is a Scrabble word!

Letter values in Scrabble US: P 3, L 1, A 1, C 3, E 1, B 3, O 1, S 1.

Is it a valid word?

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

an innocuous or inert medication; given as a pacifier or to the control group in experiments on the efficacy of a drug
(Roman Catholic Church) vespers of the office for the dead