This article applies to organisations with a Cloud setup, and those with a 'Hybrid' setup (both On-Premise Appliance and Cloud).
You can apply different Web Filter Policies to your users when they're offsite using any IP other than your organisation’s.
Step 1: Create a Location for anywhere but onsite
Create a Location Object, and exclude your organisation’s public IP addresses.
Step 2: Manage your Web Filter Policies
Create or edit Web Filter Policies to apply them when students are not onsite. In the Where field, use the Location created in Step 1.
Move these Web Filter Policies that block any websites onsite that should be allowed to users offsite.