As was highlighted above for the key-visual I've decided to go with the graphic idea - stickers. Not only it works well with the big and bold typography, it also fits well to the audience and personality of the brand being bold, playful and friendly. Also it allows to use stickers in many forms e.x laptop stickers for students, pins, bags e.t.c.
More to that, what's written there on the stickers, wasn't chosen randomly, each sticker - is a student. If you pay close attention each sticker has different levels of math knowledge from easy 3*3 to hard things like integral D(x). The idea is that all level teenagers are welcomed from the very newbies in Math (1st grade) up to 11th grade students.