Google have a detailed guide here

We've created a simpler guide with some recommendations below:

Firstly create a group of users in google for all of the office admins and other users permitted to share private data


1- Navigate to admin.google.com

2- Select Security>Data Protection

3- Select Manage Rules

4- Select ADD RULE and choose ‘New rule from template’ (its a good place to start)
Select ‘Prevent PII information sharing (UK)’ from templates

5- You can edit this by editing the Name* and Description as screenshot

6- Select Scope to decide what to restrict and if you want to bypass the rules for a specific group or OU e.g officeadmins@ group or an office@ group for example
Select 'Organisational units and/or groups’- we are going to choose all OUs as screenshot below

7- then exclude a group of exempt users e.g. officeadmins@ as below

8- Click the blue DONE button Bottom Right to add some conditions- Lots are pre-added e.g. NI number, NHS number, Drivers license numbers etc. via the template that we previously selected- You can edit the conditions on that page and select the likelihood of the data leak- for most schools this will be low BUT set as required. You can also select minimum unique matches and minimum match count these are default 1
Once you have added all Conditions click CONTINUE to add Actions and Alert

9- Select the dropdown under Actions and decide to Block external sharing, Warn on external sharing or Disable download, print, and copy… as below

10- Select ‘Send to alert centre’ and ‘Send email notifications’ either tick All superadmins though we think this may be too many people - instead Add an email recipient who is responsible for Data protection - We have in this case selected our test mentor

11- Select CONTINUE where you’ll see a preview of the rule and can select to CREATE the rule

12- You will now see that the Rule has been created and screenshot

You can now go back to the Data Protection Rules page and create more rules if required- e.g. sharing bank details, credit card details etc .