Yes, EXTENDS is a Scrabble word!

Letter values in Scrabble US: E 1, X 8, T 1, E 1, N 1, D 2, S 1.

Is it a valid word?

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

extend in scope or range or area
stretch out over a distance, space, time, or scope; run or extend between two points or beyond a certain point
span an interval of distance, space or time
make available; provide
thrust or extend out
reach outward in space
offer verbally
extend one's limbs or muscles, or the entire body
expand the influence of
lengthen in time; cause to be or last longer
extend or stretch out to a greater or the full length
cause to move at full gallop
open or straighten out; unbend
use to the utmost; exert vigorously or to full capacity
prolong the time allowed for payment of
continue or extend
increase in quantity or bulk by adding a cheaper substance

Also: stretch out, put out, hold out, stretch forth, poke out, reach out, draw out.