SAN FRANCISCO (AP) — Schools across the United States are facing shortages and long delays, of up to several months, in getting this year’s most crucial back-to-school supplies: the laptops and other equipment needed for online learning, an Associated Press investigation has found. The world’s three biggest computer companies, Lenovo, HP and Dell, have told school districts they have a shortage of nearly 5 million laptops, in some cases exacerbated by Trump administration sanctions on Chinese suppliers, according to interviews with over two dozen U.S. schools, districts in 15 states, suppliers, computer companies and industry analysts. As the school year begins virtually in many places because of the coronavirus, educators nationwide worry that computer shortfalls will compound the inequities — and the headaches for students, families and teachers.