YARMOUTH — Students from North Yarmouth Academy participated in a student-led walkout Friday morning, joining their counterparts at schools around the country in marking the 19th anniversary of the fatal shootings at Columbine High School in Littleton, Colorado. The 1999 shootings at Columbine, in which 12 students and one teacher were killed, marked the beginning of an era of deadly school shootings. More than 100 NYA students walked out of class and lined up along Main Street for 13 minutes to support efforts to end gun violence in schools. “Instead of taking a certain stance over legislation, our message is that no matter what, school shootings need to end,” student leaders said in a statement. “Seventeen people, between students, teachers, and faculty, lost their lives around two months ago in Parkland, Florida, in a school shooting.