eSpark provides lots of math and reading interactives for up to grade six, though they would also be useful to secondary ELLs.

The eSpark Lite version is free, and seems fine to me, but you can also purchase the premium version.

It seems to be very similar to the free site SplashLearn. I like that site, and my students seemed to like it last year, too.  However, as far as I could tell, students could only use interactives assigned to them – they couldn’t just choose whichever activities they wanted to try (perhaps that is no longer the case?).

I just like to have a variety of sites that students can use and where they can have a lot of choice, so SplashLearn didn’t work for me – I just don’t have the time to make individual selections.

It appears to me that eSpark does allow that individual choice, even with the free version.  I’ll report back on how it works, or doesn’t work, for my students this year.