Is life a school?

I currently reading a book by Christopher Bache called Lifecycles: Reincarnation and the Web of Life (1991). This book is interesting because even though it supports the idea of reincarnation, it rejects the idea that humans can reincarnate into 'lower beings' such as animals. Bache remarks:


Some cultures even constructed an elaborate system that tied specific moral failings to specific animal incarnations. This may be an effective method for teaching moral behavior to children and for reinforcing it in adults, but it is not a philosophically adequate concept of reincarnation (p.58)


Bache furthermore goes on to explain his remarks, stating "Once one is operating within the context and resources of human consciousness, all of one's lessons will take place in that context" (p.59). This is very different from Buddhist teachings, which have always suggested that life itself is a circle, where beings can always regress to animals or ghosts. I tend to wonder, which account is correct?
    I am not too sure at this point if I can safely say that I will be a human in the next life. Many Buddhist traditions describe how difficult and rare it is to even achieve a human form. Not only this, but I am also inclined to suspect that all the sentient beings are on a spectrum. While I can say that there are elements of me that are human, there are also aspects of myself that are ghostlike and animal-like. To say that these forms have been transcended by human forms seems a bit of a stretch. It also subtly anthromorphizes, by holding the humans as a privileged class of beings.

Bache, C.M. (1991). Lifecycles: Reincarnation and the Web of Life. New York: Paragon House.