I teach 2nd grade kids with a very wide age of abilities – granted they are all the same chronological age! – and my system in both math and reading revolves around “centers” and guided groups. The “centers” are activities that the students can do independently, while I work with small groups of 4 or 5 kids for 15 to 20 minutes of targeted instruction (in your case it could be 2 or 3 students for 12 to 15 minutes so you could see them all in one hour.) We have a centers rotation, so each group of 4 kids does a different center each day, mostly because some centers can only accomodate 4 kids.
Reading centers include:
1) A listening center (4 kids at a time listen through headphones to a book on tape while reading along in the hard copy of the book, and then complete a worksheet or graphic organizer about the story. With extra time they rewind the story and listen to it again.) For your kids the story could be in French. This is nice because all ages of kids could listen to the same story, with 2 or 3 different worksheets that are age/ability appropriate. I make a folder to keep at the listening center and tell the kids to find the worksheet with their name on it.
2) A word sort (For example: pictures of words using the short A sound and words using the long A sound. The kids cut out the pictures, sort them by sound, and glue them into a notebook.) Word sorts don’t have to be pictures, but can be used for phonics/word skills (past tense verbs vs. present tense, e.g.) and concepts. So in French they could sort food words vs. clothing words, or whatever sets of vocabulary you want them to work on. I usually differentiate these by giving each kid a packet of word sorts at his/her level. They know when it’s their day to do word sort, they tear off the top page from their packet. So a 5 year old would have different sort (probably mostly pictures) from a 10 year old.
3) Partner reading. (Read with a buddy.) Again – this is easily differentiated because students read books at their own levels. Obviously your books would be in French. You could select a bin of books for each level/age group ahead of time.
4) Computers (do you have computers?) Four kids at a time use headphones to work on various software/websites, with headphones. I don’t know any French ones, but I’m sure there are things out there. Each kid from the group of 4 is assigned a computer, so I can set it up ahead of time with the appropriate software for his/her level.
5) Sight word flash cards. Your cards could be vocabulary, with the English word on one side and the French word on the other. Older kids could “test” younger kids who are still non-readers, by showing them a picture, with the French word on the back. Or a simple memory game, with the word on one card and the picture on another, and with all the cards face down the kids have to try to turn over a match. After a short game like this I would usually ask the kids to write sentences using those words, or a paragraph for the older kids.
6) Choice writing. Students can write whatever they want and share it with a partner. Obviously your kids would write in French.
Anyway – I’m sure this gives you the idea. Meanwhile, you are calling several kids back at a time who have similar learning needs and working with them for a concentrated period, then calling several more while the first group returns to their centers. Differentiating like this is definitely a lot of advanced preparation, but once the system is up and running I have found that I can spread out the prep and it is not too bad. It takes some focused teaching of expectations for independent work times, and you’ll develop your own systems – e.g., I have a small lamp that I turn on when I am working with a guided group, and the rest of the class knows that they may NOT interrupt me when that lamp is on but must work together to answer their own questions and solve their own problems. This way the flow of instruction in the guided group is maintained. But that small group time with the teacher is so necessary in a class as widely spread as yours sounds. Good luck!