Most children in Beijing will not return to school next week as originally planned, Chinese officials said on Saturday, after an emerging Covid-19 outbreak prompted authorities to partly reverse a decision to resume in-person teaching. China is the last major economy still committed to a zero-COVID strategy, stamping out new cases with a combination of targeted lockdowns, mass testing and lengthy quarantines. But virus clusters in recent months have put that approach under strain. The megacity of Shanghai was forced into a grueling months-long lockdown and in the capital Beijing, schools were shuttered and residents were ordered to work from...