When my son was learning English, I observed that reading on the appropriate level was tremendously important for his learning. But in his school French, they m

When my son was learning English, I observed that reading on the appropriate level was tremendously important for his learning. But in his school French, they mostly do conversation and a bit of writing but not much reading. I tried to find some good reading sources in French like the Reading A-Z in English (not only has leveled reading but also audio) but so far not much. Can anyone recommend some good sources (he is 15)? Thanks!