Hi mom77 - welcome to the site! Have you asked the teacher how the levels and books are determined? It may be that they test regularly, and based on the results your son is getting books at his level. I'm not familiar with the Guided reading levels, but I guess if I were you, I would ask the teacher how she determines what is a just-right book for your kiddo. I have used the 5-finger method, where my kiddo read a page, and if he didn't know more than 5 words on the page (or was it 5 or more?), the book was too difficult, but fewer than 4 unfamiliar words was just right, to introduce new words. Some other methods seem to favor easier books for kids until they become confident readers.
One difficulty at this age, which you mentioned, is the size of the font and number of words on a page. You could mention this is a problem to the teacher, and maybe she can recommend some books at your son's level with bigger fonts/fewer words per page. Geronimo Stilton, if I remember, was an easier read at that time for my son because there were plenty of fun illustrations on the page along with words.
Anyway, I would mention all your concerns, plus the level of books your child comfortably reads and the difficulties with small fonts, to your teacher and see what sorts of ideas she has.
