[tor-talk] hierarchy anonymity

[Jonathan Wilkes]

Hi Tor,Suppose there are twitter users @Alice000... at Alice999 who all know each other's public key.  One of them is 
a teacher of an online security class.  The rest are students.
The class consists of the teacher sending the students a link to a Wikipedia page each day, for an entire year.  Each day every member of the class (including the teacher) must visit that Wikipedia page in the clear.  The teacher may only communicate with the class using Twitter (though the tweets may be encrypted using students' public keys).
Is there an extant messaging protocol that would hide the student/teacher hierarchy if all communication metadata is 
public?
-Jonathan