Academy District 20 will receive $42.7 million from the U.S. Department of Defense to help rebuild and expand Douglass Valley Elementary School, the military announced on Thursday. The cost of the project is expected to total $54.1 million, and once construction is finished, the school, located on the U.S. Air Force Academy base, will offer classes to students in prekindergarten through eighth grade.   The D-20 school is eligible for the grant through the Department of Defense’s Public Schools on Military Installations (PSMI) program. The program covers 80% of funding for major rebuilds or renovation projects for schools in need on military installations, with local school districts paying the remaining 20%.…