Reactivity of chloro benzene towards ArSN reactions is almost same as that of 

(A) The negative charge delocalizes at ortho and para positions. 

Presence of EWG (-NO₂) stabilizes the carbanion.

(B) $\because$ negative charge is not delocalized at meta position,

-NO₂ group has almost no effect when present at meta position.

Thus m-chloro nitro benzene is almost as reactive as chloro benzene.