Yes, RACISM is a Scrabble word!

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

Is it a valid word?

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

the prejudice that members of one race are intrinsically superior to members of other races
discriminatory or abusive behavior towards members of another race

Also: racial discrimination.