A mother whose 6-year-old son was killed in the Sandy Hook school shooting said Wednesday that such massacres are preventable.Scarlett Lewis' 6-year-old son, Jesse, was killed in the Sandy Hook shooting almost 10 years ago. She said Tuesday's shooting at an elementary school in Texas was reminiscent of what her family went through."It is heartbreaking," she said. "It is something that no parent should have to go through, and quite frankly, they don't have to. Every school shooting is preventable."Lewis spoke Wednesday with 1,400 students at Londonderry High School in New Hampshire, a pre-planned discussion of her Jesse Lewis Choose Love movement."If the shooter had been able to give and receive nurturing, healing love, the tragedy would never have happened," she said.She advocates for character development and social and emotional learning. "These are absolutely essential life skills that we need to be able to have healthy relationships, to be able to manage our emotions, to be able to face difficulty in our lives," Lewis said.The program calls for everyday modeling and practicing of courage, gratitude, forgiveness, compassion and action."Schools with culture who are connected and loving and have a lot of belonging are going to reduce and prevent those grievances that escalate into an attack," she said.Lewis talked to the students about the courage to speak up, both to ask for help for themselves and to spot the need in others."They're usually talking about what they're going to do," she said. "We need to believe them, and we need to act on it."Lewis said the timing of her visit, on the heels of another tragedy, was a call to action for people of all ages.