Add a another Joomla (Delegated) Administrator

Add a new Joomla "Administrator" to the site

Person has the same full administrator site access/ control that the school MIS administrator has

This is usually handled by the MIS administrator. Log into their MIS portal and delegate these permissions by,

Clicking through the "Administration >> Manage School >> Delegate Tasks" TABs path
Add in other persons to the list (via MIS ID and only school MIS members)
Select the "Edit Portal Contents" checkbox beside the users they want to be "Administrators"
Click on the "Submit" button to save.