Yes, PUNKS is a Scrabble word!

Letter values in Scrabble US: P 3, U 1, N 1, K 5, S 1.

Is it a valid word?

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

a youth subculture closely associated with punk rock music in the late 1970s; in part a reaction to the hippy subculture; dress was optional but intended to shock (plastic garbage bags or old school uniforms) and hair was dyed in bright colors (in Mohican haircuts or sometimes spiked in bright plumes)
an aggressive and violent young criminal
substance that smolders when ignited; used to light fuses (especially fireworks)
material for starting a fire
a teenager or young adult who is a performer (or enthusiast) of punk rock and a member of the punk youth subculture
rock music with deliberately offensive lyrics expressing anger and social alienation; in part a reaction against progressive rock

Also: strong-armer, punk rocker, punk rock.