As a public sector body, your website has to be accessible, but at the same time, as a school, you are partially exempt.
The government guidance explains that:
All public sector bodies, have to meet the [2018] requirements, unless they are exempt.
It also states that schools are partially exempt:
Primary and secondary schools or nurseries - except for the content people need in order to use their services, for example a form that lets you outline school meal preferences.
However, even if your site is partially exempt, there is a mandatory requirement that you publish an accessibility statement:
Partially exempt organisations would need to publish an accessibility statement on their website or mobile app.
The accessibility offering applied to all Juniper Websites enables you to meet the minimum statutory obligations.
Updated