“[It’s important] to get in with students and understand what they now know and can do and begin to chart out a path for individual students for how they can begin to recover whenever learning might have been lost during this period,” said Chase Nordengren, a research scientist with the Portland, Ore.,-based education assessment group NWEA.

The amount of learning loss over the past year has not been as significant as researchers anticipated, according to Mr. Nordengren, who credits teachers for doing “extraordinary things with the tools and the circumstances they’ve been given.”