The school channels (group IM, notices, infohub) are for school business and activities only.
Everything else is SPAM. No exceptions even if:
a) your tier date is coming up and you have to sell that parcel
b) you think it's a good idea
c) you are drunk
d) you think you're God's gift to the world and can do no wrong
e) you are a former teacher
f) all of the above