Yes, PEDERASTY is a Scrabble word!

Letter values in Scrabble US: P 3, E 1, D 2, E 1, R 1, A 1, S 1, T 1, Y 4.

Is it a valid word?

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

sexual relations between a man and a boy (usually anal intercourse with the boy as a passive partner)

Not playable in Scrabble US: PAEDERASTY.