The case for mass Covid screening in schools has not been made Every attempt to keep schools open is to be cheered but screening programmes have ethical and evidential issues that must be addressed Screen test: a young girl is checked for Coronavirus in Germany Credit: Getty Images “If screening is worth doing, it’s worth doing correctly.” So says screening expert Margaret McCartney, explaining in the BMJ that mass screening programmes can generate harms as well as benefits. This is why many screening programmes - for breast cancer, say - have taken decades to get off the ground, and why for some serious illnesses there’s still no national programme.