Kelly Mill Elementary School has been tagged with graffiti — on purpose. During spring break, Atlanta artist Corey Barksdale spent about 20 hours spray-painting the media center with his colorful, uplifting design.“Just to have that huge big white back wall, to me, we had to do something on that wall that goes with the vision we have here and the theme we’ve already got going in the media center,” said Greg Walkup, educational technology specialist, who came up with the idea. “We want it to be a collaborative where kids are talking in here ... we just wanted to create a space where they’re just comfortable, where it’s inviting and inspiring.