Kidnapped Ukrainian children are being sent to Russian “re-education” camps — where they are kept in prison-like conditions, forced to watch Russian propaganda, beaten and subjected to sexual violence, according to parents and activists. Inessa Vertash, 43, hasn’t seen her 15-year-old son, Vitaliy, in five months — ever since he left on what was supposed to be a two-week trip to a camp at the urging of his school teacher. It was billed as a retreat to escape the fighting. “I told her I wanted to think about it but she said there’s nothing to think about, they were leaving...