Yes, COLLARS is a Scrabble word!

Letter values in Scrabble US: C 3, O 1, L 1, L 1, A 1, R 1, S 1.

Is it a valid word?

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

a band that fits around the neck and is usually folded over
(zoology) an encircling band or marking around the neck of any animal
anything worn or placed about the neck
a short ring fastened over a rod or shaft to limit, guide, or secure a machine part
the stitching that forms the rim of a shoe or boot
a band of leather or rope that is placed around an animal's neck as a harness or to identify it
necklace that fits tightly around a woman's neck
a figurative restraint
the act of apprehending (especially apprehending a criminal)

Also: shoe collar, dog collar, taking into custody, pick up.