I've been trying different workbooks/websites also for the students I teach in an after-school program. We have tried various workbooks like Singapore Math, IXL, Beestar, Kumon etc. Although my youngest student is in 1st grade you can still tell that students have to be really interested in the subject or they get tired of trying to learn the concept. It is also helpful when you present the same concept in different ways. I would definitely figure out what their learning style is but Beestar really did help my students stay interested because they can see their progress compared to other students. They worksheets are also free which really helps with schools on a budget. Most importantly the students are driven to learn after using this website.