Yes, PREFORMATION is a Scrabble word!

Letter values in Scrabble US: P 3, R 1, E 1, F 4, O 1, R 1, M 3, A 1, T 1, I 1, O 1, N 1.

Is it a valid word?

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

a theory (popular in the 18th century and now discredited) that an individual develops by simple enlargement of a tiny fully formed organism (a homunculus) that exists in the germ cell

Also: theory of preformation.