Yes, CIRCUSES is a Scrabble word!

Letter values in Scrabble US: C 3, I 1, R 1, C 3, U 1, S 1, E 1, S 1.

Is it a valid word?

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

a travelling company of entertainers; including trained animals
a performance given by a traveling company of acrobats, clowns, and trained animals
a frenetic disorganized (and often comic) disturbance suggestive of a large public entertainment
(antiquity) an open-air stadium for chariot races and gladiatorial games
an arena consisting of an oval or circular area enclosed by tiers of seats and usually covered by a tent
a genus of haws comprising the harriers

Also: genus circus.