The best elementary school grammar textbook

Hi! I'm Alex from Italy, and I'd like to know your opinion about English grammar textbooks. I'm not talking about books for foreign students, I'm interested in finding out which are the most popular ones for the native speakers. In the context of a British elementary school, which textbook(s) should a teacher choose to help young students improve the knowledge of their language? For instance, would Betty Schrampfer's books be ok for this purpose? I know there can't be an only and definitive answer to this question, that's why I'd like to get many so that I can compare them! :-) Thanks everybody!