1. After signing into your teacher account, click the "Settings" link in the left sidebar.
2. Select the "Individual Student Settings" tab at the top of the page.
3. Click the box to the left of the student(s) name that you'd like to adjust.
4. Select the "Update Settings" button. 
5. Enter the desired amount of time until idle in the "Practice Idle Time” box.
6. Click the "Save" button.

Please note that you can select the "Save and Close" option after updating settings to return to the student selection menu.