The leaderboard can be found within the Friends section of the app and is accessible by tapping on the arrow in the upper left hand corner of the Learning Zone and selecting the Friends option.
If your child has a school subscription this feature may or may not be enabled by the class teacher. If it is enabled, children in the class will be able to view their friends' stars for the last 7 days, stars for the entire length of time they've spent on Doodle, current streaks and all time streaks.
Along with classmates, any siblings who are linked to the same parent account will appear within the leaderboard. Only siblings will be able to view each other's data within their leaderboards and this data will not be visible within classmate accounts.