To merge duplicate pupil accounts you need to be an admin on the account.
Please click on 'all pupils' and then use the search bar to look for the duplicate accounts, or click on the 'name' heading so the pupils are listed by their name, this makes finding duplicates easier.
Click on the square box to the left of the 2 accounts and then the merge button is available.
Click on merge and you can then choose which account to keep as the master account.
When you have duplicates you need to decide which of the accounts you wish to keep. This is often the one that the pupil has already used so has points, an updated avatar etc.
Ensure that the green surround is around the account that you wish to keep and then click merge.