Step 1) Make sure app (e.g. Dreambox Math) you're trying to use is the only open app
When other apps are open they use a considerable amount of memory and power that can affect students' experience when playing DreamBox. To close all other apps, click the Home button 
twice. All open apps are magnified. To close an app, touch and slide it to the top of the screen. Do this with each open app except for DreamBox Math. Tap the DreamBox Math app to begin playing again.
Step 2) Reboot your iPad
Just like a computer, if an iPad has been used continuously, it can affect the device's performance. You may want to try rebooting your iPad. To reboot your iPad, press and hold the Sleep/Wake button until the message slide to power off appears on your screen. Slide the power icon to shut down your iPad. Wait at least ten seconds, then press and hold the Sleep/Wake button or Home button to restart your iPad.
Step 3) Launch the app again