Many core Logic of English materials are used in both Foundations and Essentials, so those who are moving from Foundations to Essentials do not need to repurchase them a second time.
The Essentials 1-7 After Foundations Set is a special discounted package for those who have completed Foundations and are continuing to Essentials. With this set, they can have the benefit of a discounted bundle without repurchasing items they already own. The set contains all of the new items that those who already have the core supplements from Foundations need in order to teach Lessons 1-7 of Essentials.
The Essentials 1-7 complete sets, on the other hand, contain everything needed to start Essentials: all the books and cards in the Essentials 1-7 After Foundations Set, PLUS a number of required items that are also used in both Foundations and Essentials, like Basic Phonogram Flash Cards, Game Cards, and the Phonogram & Spelling Rule Quick Reference. The complete sets are designed for those who are new to Logic of English. (Choose from the Essentials 1-7 Spelling Set for students who are already reading fluently and will be doing Essentials to focus on spelling mastery, or the Essentials 1-7 Struggling Reader Set for struggling readers.)