Yes, STOOPED is a Scrabble word!

Letter values in Scrabble US: S 1, T 1, O 1, O 1, P 3, E 1, D 2.

Is it a valid word?

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

bend one's back forward from the waist on down
debase oneself morally, act in an undignified, unworthy, or dishonorable way
descend swiftly, as if on prey
sag, bend, bend over or down
carry oneself, often habitually, with head, shoulders, and upper back bent forward

Also: lower oneself, round-backed, round-shouldered.