Yes, ALLIANCES is a Scrabble word!

Letter values in Scrabble US: A 1, L 1, L 1, I 1, A 1, N 1, C 3, E 1, S 1.

Is it a valid word?

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

the state of being allied or confederated
a connection based on kinship or marriage or common interest
an organization of people (or countries) involved in a pact or treaty
a formal agreement establishing an association or alliance between nations or other groups to achieve a particular aim
the act of forming an alliance or confederation