By default when you take photos you can see they are getting stored in two places, one is your photos and other is the photo stream. Photo stream is the one which uploads the photos automatically and send them to all of your iCloud devices when connected to Wi-Fi. When you want to stop sharing this you can do by following the below steps,
Go to Settings-> Photos & Camera-> switch off the My Photo Stream. When you do this it asks for confirmation – Turning off Photo Steam will delete all Photo Stream photos from your iPad. Not to worry as this might delete all of the photos from your iPad, it won’t. (If you are still not happy with my statement you may very well take a back up of the photos before you continue)
So here is the screen when you switch off the My Photo Stream, tap Delete Photos. Now all the photos from the Photo Stream(Photo Stream only) get deleted.