Organizations with multiple schools or subdomains often have distinct groups of admins responsible for different sections of the overall site. Rather than giving all site admins full access to every section, it's possible to allow admins full access to the pages that they maintain, and only limited access to pages in other areas.
This is done by editing the Composer Permissions for each Site Admin group.
Site Admin Groups
All site administrators must belong to one, and only one, Site Admin group. Site Administrators can edit admin group membership by selecting "Admin Users" from the People menu in the Composer left navigation bar.
When viewing Site Admin groups on the Admin Users screen, click on the the gray chevron button to the right of an admin's name to open up a flyout menu where you can move the user to a different admin group, if necessary.
After ensuring that all admins are sorted into the right groups, set the access rights for those groups in Composer.
From the Composer main menu, select "Permissions" to edit access levels for each Site Admin group. Use the dropdown menu in the "Pages" column there to set the level of access for the members of each Site Admin group.
Limiting Access to Site Sections
In Composer, the rights granted on the "Permissions" screen as described above are default rights. They control the level of access for members of each Site Admin group throughout all Composer pages, site-wide.
Restricting access to site sections is done by navigating in Composer > Pages to the pages to be restricted, and manually adjusting the rights levels of specific Site Admin groups to override the default. This can mean either elevating default rights to allow editing, or removing default rights to prevent editing.
In practice, one top-level Site Admin group should have full administrative rights. In Composer, the "Admin" permission level includes all View / Edit / Publish / Delete rights, as well as the right to edit other Site Admin groups' permission levels. Only top-level administrators should belong to this group.
Other site admins should belong to groups that are specific to the sections of the site that they maintain.
These section-specific groups should be given the "View" right on the Composer Permissions screen. This will allow them to access, but not edit, all site pages. (Alternatively, the "View and Edit" right allows admins to change site pages, but not to push those changes to the live site.)
Adjusting Site Page Permissions
To grant editing access, navigate to a page in the site and click the gear icon in the bottom bar to open up the page settings.
Select the "Permissions" tab.
As on the Composer > Permissions screen, each Site Admin group is listed. Use the dropdown menu next to each one to override their default permissions and set a new permission level for this page and all of its child pages.
Permissions set on a parent page will always cascade down to all of its child pages automatically. Child page settings cannot be more restrictive than parent page settings. The only exception to this rule is the "Not Allowed" setting, which can be employed to block editing access to a page entirely for members of the selected admin group.