Is it safe for children to return to school while the coronavirus is on the loose? That depends on what’s likely to happen if a student becomes infected. Will the virus jump to his classmates, who could then fuel its spread throughout the student body? Will it find its way to his teacher and hitch a ride to the break room, putting the faculty on campus at risk as well? Scientists don’t have definitive answers to questions like these — and they probably won’t for quite awhile. Schools are coping with this uncertainty in different ways. In Southern California, the state’s two biggest districts — Los Angeles Unified and San Diego Unified — said they would begin the new school year with full-time distance learning.