We are switching to Elemental Science this year, and are starting with Biology for the Logic stage for my 5th grader. I just spent a lot of time reviewing the text, and am really excited about it ... very compatible with WTM approach, but a lot of the work already done for me. http://elementalscience.com/collections/biology-for-the-logic-stage/products/biology-for-the-logic-stage-printed-combo I was initially nervous about buying all the "reference" books, but was able to find most of them VERY cheap on Amazon.com used books. The Elemental Science Amazon Store link made it VERY easy to find the right versions of the books recommended in the text. http://astore.amazon.com/elemescien-20?_encoding=UTF8&node=8 We used NOEO last year, same ideas, but I like that this has more reference material incorporated. Colleen