Yes, ADOPTION is a Scrabble word!

Letter values in Scrabble US: A 1, D 2, O 1, P 3, T 1, I 1, O 1, N 1.

Is it a valid word?

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

the act of accepting with approval; favorable reception
a legal proceeding that creates a parent-child relation between persons not related by blood; the adopted child is entitled to all privileges belonging to a natural child of the adoptive parents (including the right to inherit)
the appropriation (of ideas or words etc) from another source