If you are interested in Montessori and the introduction to grammar, then I have a post over on MOC on how to do it. When I first discovered Montessori I read The Science Behind The Genius, which is an excellent book and really laid it out why Montessori's theories were so spot on.
I fell in love with various parts of her work, the math work is nothing short of genius and I really wish I had be taught that way. The grammar work too is a great way to approach the subject, we have been a bit slack as of late but Ebi-kun really enjoys doing the work so we made a deal to do some grammar work every week. Now it the tough part, of keeping his level up as the Japanese school work increases.
The introductory lesson and everything you need is over HERE. If you have a bilingual child who is in school, how do you go about keeping their language levels up?