Yes, REALISM is a Scrabble word!

Letter values in Scrabble US: R 1, E 1, A 1, L 1, I 1, S 1, M 3.

Is it a valid word?

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

the attribute of accepting the facts of life and favoring practicality and literal truth
the state of being actual or real
(philosophy) the philosophical doctrine that physical objects continue to exist when not perceived
an artistic movement in 19th century France; artists and writers strove for detailed realistic and factual description
(philosophy) the philosophical doctrine that abstract concepts exist independent of their names

Also: naive realism.