Lab Scheduler is a neat Google Sheets Add-on that enables you to easily create and maintain a lab or room reservation system for your school. It is designed for schools that use a labeled block schedule (for example, the high school in my district uses "period 1" through "period 8" even though there are only four periods in a given day).
Once you have added Lab Scheduler to your Google Spreadsheet it will walk you through the process of creating blocks of time and lab/room space in your spreadsheet. You can set your Lab Scheduler to maintain a preview of as many dates as you like. The preview is what people will see when they want to make a reservation. Share the spreadsheet with your staff and they can reserve a block of time in it.
Applications for Education
Lab Scheduler could provide your school with a good way to keep track of who is using which rooms when. If you have multiple rooms to schedule, you could create a few spreadsheets with Lab Scheduler then put all of those sheets into one shared Google Drive folder.