On the Setup tab you edit six lists once, days, periods, classes, subjects, teachers and rooms, and every dropdown in the workbook reads from them. On the Timetable tab you build the plan one lesson at a time. Two columns watch every slot: Teacher clash counts how many lessons put the same teacher in the same period on the same day, and Room clash does the same for rooms, so a double-booking turns red before it ever reaches a bell.
Class View pulls it together: pick a class and read its whole week as a periods-by-days grid, ready to print. The Workload tab counts each teacher's lessons per week for you and shows how busy each room is. Yellow cells are the only ones you type in; every other cell is a locked formula, so the maths cannot break. It opens in Excel, WPS or Google Sheets, so you can plan on a laptop and check it on your phone.