Online books for my ESL Class

I am asking for your help in funding Raz-Kids for my students this year.   I teach English as a Second Language.  I need books that will help build vocabulary as well as help students improve their reading skills.  The students and I love Raz-Kids.   It is an award-winning resource that provides a library of differentiated books at 29 levels of difficulty students use to practice reading in school or at home.   The faster that I can pay for this resource, the sooner my students will be reading these wonderful books.  I appreciate any amount of help you can offer.   Thanks!