Parents of children with developmental and psychiatric problems have pushed to gain more access to mainstream schools and classrooms for their sons and daughters. One unfortunate result, some experts say, is schools’ increasing use of precisely the sort of practices families hoped to avoid by steering clear of institutionalized settings: takedowns, isolation rooms, restraining chairs with straps, and worse. No one keeps careful track of how often school staff members use such maneuvers. But last year the public system served 600,000 more special education students than it did a decade ago, many at least part time in regular classrooms. Many staff members are not adequately trained to handle severe behavior problems, researchers say.