I am developing a new activity for one of my classes that will utilize breakout rooms. It is/was my understanding that when you use WebEx integrated telecom, the conference call will be broken up into the small groups, i.e., those in breakout room a won't hear the conversations in breakout room b, and vice-versa. However in testing the exercise this afternoon, this was no the case, the call was never split up, and no one was ever prompted to have the call split. I've attended sessions where the call split up and I remember having to respond to a check box to split off from the main call. 

The only thing I had done differently today was to use and instant session, and then started the conference call from within the session by clicking Communicate > Join > Teleconference. Does this make a difference?

What gives?

Are these the steps you took to start your teleconference during a breakout session?

If you are in the main session teleconference when a breakout session starts, the following dialog box appears.
 

If you select Yes, you are switched to a breakout session teleconference. 

If you select No, you will not join the breakout session teleconference at this time. However, you can join later by selecting Switch to Breakout Teleconference from the Communicate menu.

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To use an Integrated VoIP conference, your computer must meet the system requirements for Integrated VoIP. For details, see Starting an Integrated VoIP conference.

When you start an Integrated VoIP conference in a breakout session, all the Integrated VoIP options that the host set up in the main session apply to the breakout sessions.

To start an Integrated VoIP conference in a breakout session:

1. In the Breakout Session window, on the Communicate menu, point to Integrated VoIP, and then choose Start Conference.
2. Optional. To use the Volume dialog box to adjust the volume of your speakers or microphone or to mute or unmute your speakers or microphone, point to Integrated VoIP, and then choose Volume.
3. Optional. To use the Audio Setup Wizard to set up audio options, choose Audio Setup Wizard on the Communicate menu.
   The following occur:
   • The Volume dialog box appears, on which you can adjust the speaker or microphone volume.
   • A microphone symbol appears to the left of your name in the participant list on the Breakout Sessions Manager panel.
     
     Note:  The microphone symbol flashes to indicate which participant is speaking during the breakout session.
      
   • The Join Integrated VoIP Session message box automatically appears in the Session window for each participant in the breakout session whose computer has a supported sound card. Participants can then choose to participate in the Integrated VoIP conference.

To find further help information regarding the WebEx service please do the following:

Navigate browser to your WebEx site (Example: https://sitename.webex.com).
Select the service you are using by clicking on the link at the top of the page (Example: Meeting Center, Training Center, Event Center).
Click on the Assistance link located on the left hand navigation bar.
Click on the Help link.

Thanks Holly, but this is exactly the behavior I was expecting but didn't receive. I contacted my CSM yesterday evening and here's what we found:

There is a sub-conferencing option in the Super Admin page that by default is not selected. The Sub-conferencing option must be selected for the break-out conferences to occur. This setting must be made by the Super Admin, who apparently is a WebEx employee.

So there was no way for me to resolve the issue on my own. I am informed that the setting has been corrected and will be running a new set of tests this morning to verify the conference call to split up as it should. The thing that has me scratching my head is why is the default to _not_ have the call split. It seems it should be the other way around to me.