What are Custom 1/2/3 used for? Can I rename these fields?

These are the 3 default custom fields that you can import any value into. For example, you could use Custom 1 to import and store a value for Summer Born pupils.

These fields cannot be renamed, however, it is possible to create your own custom fields using Admin > Edit Pupils > Custom Fields.

Data can be then added to these fields manually in Edit Pupils

Alternatively, you can easily import custom field data by setting up a spreadsheet, adding columns for Forename, Surname, Gender, and ideally UPN as well, followed by the custom field and any other information you require.

In the 3rd step of the import, Map Data, you can select the custom field/s to map to in the 'Include As' column.