From Google Support:
"Videos in YouTube Kids
We’ve built the YouTube Kids app to be a family-friendly place for kids to explore their imagination and curiosity. Videos available in the app are determined by a mix of algorithmic filtering, user input and human review. Videos in YouTube Kids can be discovered in three ways. Some videos are pre-selected, while others are discovered by your child through search. The app can also recommend videos to your child based on what your child has watched. The pre-selected content goes through an additional level of quality control through some human review. Search and Recommended videos are selected by our algorithm without human review. Though our system has been tuned and tested rigorously, no algorithm is perfect, and even a perfect algorithm would not replace a parent’s judgement. This means that it’s possible that your child may find content in the app that you may not want your child to watch. If this happens, you can notify YouTube by flagging the video. We use these flags to improve the app.
For a more restricted experience, you can turn search off, allowing your child access only to pre-selected content. Turning search off reduces the chance of your child finding content you don’t want them to watch.
We also will remove videos from the YouTube Kids app where the creator has notified us of a paid product placement or endorsement in their video through YouTube’s paid product placement and endorsement notification tools."
