It is somehow strange that the school you are working at does not seem to have the proper student books for it students beyond the Phonics and basic literacy level. You haven't said in which part of the world that school is situated, so I can't advise you in detail. However, if I were in your situation I would do the following:

1. prepare my and supply my own material in lieu of a proper textbook lacking,
2. search the internet for material that may fit the level of my students.

You may find a wider rage of free material on http://www.englishbanana.com, but I am not sure at all whether there is anything that you would suitable; most of the material offered there is most likely more suitable for older students. But give it a try and have a look...

You could also google for "Genki software" (or similar name, I do not remember exactly); I came across that stuff in the internet a while ago, and it seems to be material with a commercial license especially for students at your age.

Third, couldn't you ask fellow teachers in your place for advice on how to find more suitable material?

I am just wondering what kind of school or "school that is leaving you alone with important things like that....

Good luck!