Photomath
Photomath is pretty awesome. (This one might be more for the parents helping with Algebra or Geometry than the kids!) You can use it to check your working on complicated math problems. It is as simple as holding up the camera to the problem and it will do the rest!
Duolingo
Our kids were told about this through school and practice their languages for 10-15 per day in addition to homework. They are always happy to do it as it is fun and feels like a game. Plus it’s FREE!
Khan Kids
One for younger kids. This fun app has cute characters and helps your kids work on Math and English skills.
Toca Boca
Another one for younger kids, and technically not an ‘educational’ app but it builds some good skills and our kids love it. There are many Toca games in the series, some are free and some you have to pay for.
Notes
Yes really! Notes on the iPhone is a really useful app, especially for those kids who have to complete lessons on paper and then hand in virtually. Notes has a feature not many people are aware of which allows you to scan documents as a pdf!
Tech Tidyup 