Jose Martins’s joy is palpable on the hot, sticky pool deck at Marshall Elementary, where the humidity is infused with the chlorine. The pool opened four days ago. Today, swimmers — some in their bikini tops — are outside waiting to get in.

Girls preen for boys in board shorts as little kids splash around in oversized goggles. Jose, who lives on Draper Street in the house he grew up in, shouts reminders to ungraceful swimmers: To go into the deep end, he yells, you must pass the swim test.