Standardized tests are returning to the nation’s schools this spring, but millions of students will face shorter exams that carry lower stakes, and most families are being given the option to forgo testing entirely. With new flexibility from the Biden administration, states are adopting a patchwork of testing plans that aim to curb the stress of exams while still capturing some data on student learning. The lenient approach means large swaths of students will go untested, shattering hopes for a full picture of how much learning has been set back by the pandemic.