The old Fifth Street School campus in downtown Las Vegas has undergone more than two years of renovation at a cost of $9.5 million. When completed this fall, the school will house something unseen there since the late 1960s, when the school stopped operating to become a courthouse annex. Students of all ages will be learning. The Nevada School of the Arts, which provides musical instruction and art classes to very young students, will be housed there. The American Institute of Architects and the city’s Cultural Affairs Division also will have offices there.