The first book that every school needs is « The Gruffalo » by Julia Donaldson. I love its dramatic intensity, and all the funny twists that convey an essential message: the tiniest mouse can outwit any monster.
The second book I recommend is «Haut les Pattes » by Catherina Valckx (available in English too). A small hamster, brave and dependable, goes on a quest to become a coy boy. Extremely funny.
The last book is « Le loup qui voulait changer de couleur » by Orianne Lallemand (avail. in English too), because we may not think we look good enough, and no one is perfect, but we could really not be otherwise. Love yourself! And keep on reading all the « Le loup » books in the series.
These three books are best for children aged 4-9 years old. I read them every single year to my Grade One students. :-)