Parents often ask me to recommend aural training or music theory apps. Here are a few of my favourites:
Better Ears Beginner: https://itunes.apple.com/us/app/better-ears-beginner/id284445260?mt=8
Music Theory Pro: https://itunes.apple.com/au/app/music-theory-pro/id390788573?mt=8
For more advanced students (above grade 3 AMEB of year 9 high school) I recommend taking music theory lessons. The Music Craft work books include aural activities & they prepare students for high school music studies. It’s a nationally recognised AMEB course & each workbook is spilt into 40 chapters - students complete 1 chapter a week to compliment their instrumental lessons.