Pennsylvania officials on Monday announced a plan to test students for COVID-19 as part of the effort to prevent the disease from forcing schools to close. The plan is voluntary, with school districts deciding whether or not to participate. In schools that participate, a contracted firm would conduct the tests weekly. In most cases, students would swab their own noses in a process that officials said is much less uncomfortable than early tests that required the swab to be inserted deep into the nasal passages. Samples would be combined into a “pooled” testing process that would not produce results for...