Definitely! The quantity discount is based on the total number of licences purchased by a single school or organisation account. (Please note that this does not apply to Bulk Buyer Accounts.) So, if a school with no licences purchases 1 licence, they will be charged at the single licence rate. If in a later order they purchase 2 further licences, this will bring the total number of licences held by that account to 3, which means that the second 2 licences will be charged at the 2-5 rate.
This applies whether the licences were purchased from AB Tutor or from an Authorised AB Tutor Reseller or from both at different times.