My photos on iCloud were deleted without my permission

iCloud is a syncing service, not a cloud archive. It will always mirror what is on all of the devices synced to iCloud. So if you delete photos from your iPhone, or any other device synced to iCloud, they will be deleted from iCloud and also from all other devices.

If it is deleted from your iPhone it is deleted from iCloud too and vice-versa.

Thumb Rules:

1. Enable  Guided Access before handing over an iPhone to kids
2. Don't share Apple IDs
3. Don't Jailbreak
4. Don't share sensitive information pertaining to your device