My son is a high school senior and we were already done with the 3rd quarter when our schools shut down. He is finishing the classes online now and the grading policy is that they cannot do worse than their 3rd quarter grade. Students have opportunities to improve their grade based on tests and participation. All his teachers (except PE and music) have arranged for live office hours, some Zoom meetings, and recorded lectures. We did set up a couple of outside tutoring sessions for math as he is taking a high level Calculus class.
His future university (Northwestern) is making all spring quarter classes Pass/Fail. Given all the dynamics of the current situation, I think that was the right way to go.