from wikipedia....
"In May, 1984 District 214 put Arlington High School up for sale and then for auction. Arlington High School closed its doors to public high school students in June, 1984. The following year in April, Christian Liberty Academy of Prospect Heights purchased Arlington High School for $1.51 million. Christian Liberty Academy continues to operate from the Arlington High School building.
Interior and exterior scenes from the 1986 film Lucas starring Charlie Sheen and Corey Haim were shot at the school during the summer immediately after its closing, including some scenes with the Prospect High School Marching Band which at that point contained former Arlington students."
so now you know! ♥