Moving children at the end of the year can be done en masse from the Administration section but you may also need to move children between classes or year groups. 

On the child profile, you should click on the pencil icon next to the student's name.

You can then make changes to the child details including the year and group they are placed in. Verify the details before saving the profile to ensure you have not accidentally made unintended changes. 

Click Save to update the profile.