An administrator's role depends on whether it's a small primary school or a large secondary school, for example, where duties will be divvied up between a team. But expect the role to cover the following:
welcoming visitors to the school and dealing with their enquiries
answering the phone
administration relating to pupil attendance
managing email/post
using IT systems to draft letters, emails, reports, newsletters
monitoring school supplies
keeping financial records
keeping paper and electronic records up to date
using reprographic equipment
ordering resources, paying invoices and banking cash
sending key educational data about the school to the Department of Education or equivalent