This is a powerful and bold visual concept with large pictures and graphical elements (geometric as well as typographic) that stimulate associations and give a stable context to the other materials.
There is a very good balance of race, nationality, gender and age: students can identify with this and also learn about cultural differences.
The digital material is well-structured for teachers who can use it to build up a school year plan; lesson plans, audio material as well as templates to copy and nicely laid-out tests contribute to lesson organization.