By default all new groups have full access rights for all teachers, i.e. any teacher may enter the group. To limit access privileges for any group:
– open the Connection Server Management Console (on Server computer click Start -> All Programs -> Net Control 2 -> Connection Server Configuration);
– on Groups tab select a group and click Access permissions button on top toolbar.
In the appeared dialog, delete All users> group from the list. Click Add button and add teacher accounts or teacher groups, which should have access to the group. Click OK.