After two weeks pass, [Hermione] once again broaches the subject of [Harry] teaching defence lessons, and Harry finally agrees to teach anyone interested in joining.
With [Hogsmeade] weekend approaching, [Harry], [Ron], and [Hermione] discuss the possibility that [Sirius] might show up, as well as the fact that a number of people seem interested in taking defence lessons from Harry.
A Secret Meeting in the Hog's Head
[Harry], [Hermione], and [Ron] make their way to the [Hog's Head], where they expect students to turn up who are interested in taking defence lessons from Harry. On the way they discuss whether they're breaking any school rules, and marvel at the atmosphere in the grungy pub.
The door to the [Hog's Head] opens and a crowd of students walks in, all to hear what [Harry] has to say about teaching them defence lessons. Despite some initial resistance, all twenty-eight of them sign up to take lessons, and gradually make their way back into [Hogsmeade].
With their fellow students gone, [Harry], [Hermione], and [Ron] talk discuss their meeting at the [Hog's Head]. In doing so, Harry and Ron learn that [Ginny] is dating [Michael Corner] - and Harry learns from Hermione that [Cho] "couldn't take her eyes off" him during the meeting, thrilling him even further.
Chapter 17 - "Educational Decree Number Twenty-Four" - In which the High Inquisitor orders all Student Organizations, Societies, Teams, Groups, and Clubs disbanded, Harry and Ron learn that boys are not allowed in the girls' dormitory, Hedwig is hurt coming back from London, and Sirius is almost caught by Umbridge in the Gryffindor common room fireplace.
The Banning of Clubs
For the rest of the weekend [Harry] is happier than he's been all year, thanks to his knowledge that his defence group is resisting [Umbridge] and the [Ministry].
[Harry] and [Ron] awaken to find a crowd in the [common room], gathered around an [Educational Decree], which bans all student organizations. Soon [Hermione] comes down as well, and they grimly head down to breakfast.
At breakfast [Harry] quickly shoos away members of his defence club who are wondering whether they can still meet, but Harry himself defiantly says that the group will continue on. However, [Angelina] arrives and make him realize [Quidditch] teams are included in the ban, and Harry agrees to continue to keep his temper with [Umbridge].
A Letter From Sirius
As [History of Magic] drones on, [Hedwig] arrives at the window, clearly injured. [Harry] asks for permission to leave class and runs to the [staffroom] to find [Professor Grubbly-Plank], who agrees to nurse Hedwig back to health, but as Harry leaves [Professor McGonagall] warns him that communication channels are being watched.