Yes, ARE is a Scrabble word!

Letter values in Scrabble US: A 1, R 1, E 1.

Is it a valid word?

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

have the quality of being; (copula, used with an adjective or a predicate noun)
be identical to; be someone or something
occupy a certain position or area; be somewhere
have an existence, be extant
happen, occur, take place; this was during the visit to my parents' house"
be identical or equivalent to
form or compose
work in a specific place, with a specific subject, or in a specific function
represent, as of a character on stage
spend or use time
have life, be alive
to remain unmolested, undisturbed, or uninterrupted -- used only in infinitive form
be priced at

Also: make up.