The feature which allowed deleting of a user profile has been de-activated recently. This has been done to prevent kids from deleting their progress and profiles by mistake. Our development team is working on this feature and we will be re-introducing this feature with appropriate checks in future versions of Splash Math Grade 1.
However, if you would want to reset all the players and start the app afresh, you can delete and reinstall the app. This would ensure all the data is reset and you can setup the app from scratch. This can be useful for teachers who need to reset the app at the end of each year to set it up for new kids.