Margaret Clark 
Aussie Angels 1: Okay Koala [EPUB ebook] 

There’s trouble in school when the Angels get a new principal and a new teacher. And it seems that suddenly Greash and Foxie are the teacher’s pets. Pests, more like it. Sneaky deeds with Feral the ferret get the twins busted, but wombats are involved in the situation too, and Mike and Meg need to find out how. Whatever the answer, you can bet Greash and Foxie are up to no good. OKAY KOALA is the first book in a series loved by children all over Australia.