Yes, WRITES is a Scrabble word!

Letter values in Scrabble US: W 4, R 1, I 1, T 1, E 1, S 1.

Is it a valid word?

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

produce a literary work
communicate or express by writing
have (one's written work) issued for publication
communicate (with) in writing
communicate by letter
write music
mark or trace on a surface
record data on a computer
write or name the letters that comprise the conventionally accepted form of (a word or part of a word)
create code, write a computer program

Also: drop a line.