By Brendan O’Brien CHICAGO (Reuters) – A Philadelphia school teacher, an Arizona teenager and a Chicago police officer were among hundreds of people struck by gunfire over the weekend, part of a relentless wave of shootings that has forced the United States to examine ways to curb gun violence. More than 124 people were killed and 325 wounded in more than 300 shootings recorded in the United States since Friday, according to GunViolenceArchive.org, a Washington D.C. non-profit that tracks shootings. The rash of weekend violence came on the heels of a series of shocking mass shootings in Uvalde…