The Elizabeth (N.J.) school district has spent more than $2 million since January 2006 to buy navy blazers, khaki pants, polo shirts, gym shorts and even socks as part of a new policy to put all its students in uniforms. The district, which serves mostly poor and minority families, has outfitted more than 9,000 students — nearly half its enrollment — so far as it phases in the uniforms a few schools at a time over five years to spread out the cost.