Some Battle Ground Public Schools students were sent home early Monday afternoon after staff at Pleasant Valley Middle School noticed a sagging ceiling in the library.As a precaution, the district decided to send home students at Pleasant Valley Primary as well, since it sits on the same property as the middle school. On Monday evening, district officials said classes will be held at both schools Tuesday. Facility crews removed a heating and cooling unit from the roof Monday to relieve stress to the structure and to inspect the area, according to a school district news release. The inspection showed that all parts of the middle school are safe, but the school’s library and media center remain closed for repairs. The HVAC system doesn’t appear to have suffered any damage, but it may not have been securely fastened in place, district spokesman Sean Chavez said. Other heating units are available to warm the school today.The incident marks the second scare the school has had with the HVAC system in the past few months. On Dec. 20, firefighters came to the school after a reported smell of smoke wafting through the gym. They determined that a filter had been sucked into the HVAC system and began burning.Pleasant Valley Middle School, which is at 14320 N.E. 50th Ave., opened in 1975, according to the district’s website.