[stanley]

I have managed to persuade my school to buy some materials for my use in class and would like to try the Let's Go series, as it has been so often recommended on this site. As anyone who has read my other posts will know, I have a wide range of abilities within each class so I only want to use the course as a guide - I will use what is relevant and supplement it with my own ideas. I have had a look at some of the workbooks (I found them gathering dust in a cupboard but have not managed to see a teacher's book. I was wondering roughly how long each level is designed to last. I teach grades 3, 4 and 5 (8 - 11 yr olds). Could anyone who uses the course let me know how long they spend on one level (book). At first glance, the workbooks don't seem to have a huge amount in them. I have each class for only 40 minutes a week and I am only teaching speaking and listening. Also, where does the series stop - intermediate? upper-intermediate? In other words, would it even be suitable for my grade 5s, many of whom speak English very well.
Thanks in advance for any input.