Ask HN: Schools are closing. Advice on teacher’s communication with students?

We’ve just been informed that my daughter’s middle school is closing as of next week. Everything will be done online but teachers are scrambling at the last minute to setup various programs with which they are painfully unfamiliar. The two platforms to which they have defaulted are Edmodo and Remind. Are there any others with more robust features but relatively easy to set up for the nontechnical person. Are Slack and Discord appropriate technically for the middle school group? Recommendations for more involved solutions are also welcomed, including any for K-12 in general.