Schools are not going to repeat for everyone, if only because it would be monumentally unfair (and counterproductive) to force students who learned the required curriculum to repeat a grade. But if you just give everyone a pass and throw students into the next grade who basically skipped a semester, that's not going to play out well either.

ADDED: What I suspect happens is that most schools bend over backwards to pass everyone they feel they possibly can and adjust lesson plans when schools come back to recognize that many students didn't really learn much the previous semester.