If you receive a notification that your iPad has not backed up in many days or weeks it is often because you do not have enough iCloud space available for the iCloud backup to run.  Apple provides 5 GB of free iCloud space so if the amount of data for the apps currently selected to backup on your iPad is more than that 5 GB of space, the iCloud backup will not run. 

You can check how much backup space an app is using or disable backup for any app on your iPad using Settings > iCloud > Storage > Manage Storage > Backups / This iPad > Backup Options.

Do not disable the backup for any app that contains important school work or notes unless you know you have that work saved somewhere else.

While any app could be taking up backup space, usually images and videos take up the most.  If that is true for you, you have three options to get your backup working again:

Option A 

If the Photo Library/Camera Roll is the issue, delete images and video that you no longer need or that you have saved elsewhere especially if you have images and video you don't need for school work. (Google Drive is a good place to put copies of images or videos since you have unlimited space there.)

Option B

Disable backup of the Photo Library/Camera Roll.  If you do this, you NEED to make sure that if you have anything important for school in Photos that you make a copy of it elsewhere. You will need to continue to do this in the future anytime you have an important image or video. For example, you could upload any very important images or video to a Google Drive folder by using the Google Drive app. Disabling the backup of Photos will not delete images or video from your iPad. However, everything in Photos on your iPad will be gone forever if you have a problem on your iPad that requires resetting it (or your iPad damaged or goes missing), and you have not backed up your images and videos elsewhere.

You can check how much backup space an app is using or disable backup for any app on your iPad using Settings > iCloud > Storage > Manage Storage > Backups / This iPad > Backup Options.

Option C

With your parents, purchase more iCloud space for your Apple ID. Apple sells an extra 15 GB of storage for $0.99 a month and an extra 195 GB of storage for $3.99/month.  This is available under Settings > iCloud > Storage > Buy More Storage.

If you would like help with any of the above, you can bring your iPad to the Taub Technology Center in the Library anytime between 8:00 AM and 4:00 PM on a regular school day.