Retain Unified Archiving provides complete and compliant archiving of Gmail and Hangouts within G Suite for Education (formerly called Google Apps for Education). According to the Gartner Magic Quadrant for Enterprise Information Management & Governance, “Retain is one of the few archiving solutions that offers native Gmail archiving support.”
G Suite for Education is free for all non-profit K–12 and non-profit higher education institutions. It provides your school with free web-based email, calendar, and document creation tools for collaborative work and study anytime, anywhere.
Google Vault is included with G Suite for Education as an archiving solution that provides email searching and exporting capabilities for Gmail messages. Google Vault has some decent archiving features. Unfortunately, those features are limited in many key areas that can put your school at risk of litigation or compliance violations and can make information governance and eDiscovery difficult.