Guided Access is a mode that keeps your iPad locked into a single app. There is a glitch associated with it, however. It’s supposed to disable when you press the home button three times. Sometimes that doesn’t happen.
What do you do then?
You will have to force a reboot. You do that by holding down the Home Button and the Power Button for several seconds. Just continue holding them down until the iPad shuts off. It should take about 15 seconds or so.
As you reboot, the guided access app will start loading again. You must press the home button to exit. After that, go to Settings>Accessibility>Guided Access>Off
Also worth noting is that if you exit guided access, but go back into the app that had it enabled, it will launch guided access again. You will have to close the app in the multitask pane as well.
Credit: OS X Daily