Yes, CONTROLLING is a Scrabble word!

Letter values in Scrabble US: C 3, O 1, N 1, T 1, R 1, O 1, L 1, L 1, I 1, N 1, G 2.

Is it a valid word?

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

exercise authoritative control or power over
lessen the intensity of; temper; hold in restraint; hold or keep within limits
handle and cause to function
control (others or oneself) or influence skillfully, usually to one's advantage
check or regulate (a scientific experiment) by conducting a parallel experiment or comparing with another standard
verify by using a duplicate register for comparison
be careful or certain to do something; make certain of something
have a firm understanding or knowledge of; be on top of

Also: hold in, keep in line, see to it.