Chicago officials cancelled classes in the nation’s third-largest school district on Wednesday amid a dispute with the teachers’ union, the latest disruption to US education and life as the omicron variant spurs a record-setting Covid-19 surge.

The move came after the teachers’ union voted late on Tuesday to return to remote learning and pushed for more rigorous safety protocols.

The rolling seven-day average number of new Covid-19 cases in the US hit 540,000, a new high for an eighth consecutive day on Tuesday. The country shattered global records for a single day with nearly 1 million new infections on Monday, according to a Reuters tally.