What it needs to install is a Google for Work profile. It will prompt you to create a partition for work apps (e.g. Drive, gMail, etc.) These work apps will then appear on your phone but stored separate from your personal apps and data. These apps will have a little orange "work lunch box" icon on them. See image below.
This way your personal data and work data are kept seperate and helps respect the boundary between the two; the school only sees work data and not your personal data. Please note, the opposite is true when placing personal data on a work device (e.g. teacher laptop). The same is also true if you decide to open personal email on a Google for Work app (e.g. Gmail).
If you decide to proceed with Google for Work, one important consideration is that the school can lock and wipe work apps data (yes, work apps only) since the student or employee placed work app/data on a personal device. At Greenwood, we have not locked a personal phone or wiped data to date. We would only do so under the direction of the Principal or from the student or employee under special circumstances.