(Portland, OR) -- A petition is circling to reinstate a popular Portland teacher who was placed on leave over an unauthorized walkout. A district spokesman says Chris Riser was put on leave Friday from Ockley Green Middle School after the student walkout last month. The protest reportedly centered on the police shooting of a 17-year-old a year earlier. "The Oregonian" reports that more than 13-hundred signatures have been gathered on a petition in an effort to have Riser reinstated. The walkout was called an "unauthorized" action not in keeping with district policies.