Quick tip here:
Another way to makle learning fun is to note themes or subjects that your kids are interested in and apply them to your curriculum.
If you have a kid who likes cars and you are studying addition, give him/her car themed addition problems.
If you have an animal lover and your are studying adjectives, have student write descriptive sentences with adjectives describing animals at the zoo. (I find that this engages the kids more than just writing sentences out of the blue).
Simple idea, but can be very powerful, insha Allah in engaging disinterested students.
Or if you have a kid who is overly obsessive about a topic and eats, sleeps, and drinks it, themes are a nice way to introduce him/her to other topics to broaden his/her horizons.