In my opinion, though others may disagree, the iPad has been crying out for a simple and effective Green Screen app since it's introduction. I won't mention any specific apps but the ones I had tried were far too complicated for Primary pupils and the activities became very teacher led. I have recently been using Green Screen by DoInk. https://itunes.apple.com/gb/app/green-screen-by-do-ink/id730091131?mt=8 with upper Key Stage 2.

What I like most is how quickly the pupils can create their videos using the app. They find the background video/image and add that into the time line. The video of the pupils standing in front of a green screen can then been filmed in real-time over the top. Videos can then be shared to the camera roll. I particularly like using the app in conjunction with apps such as I Can Present (as a teleprompt) and iMovie (to stitch videos together and add soundtrack for GarageBand)

I am looking forward to trying more Green Screen work with other age groups next term to see how they handle the app.  I am also keen to try the Touchcast app as it includes many of the features of iMovie, Explain Everything and Green Screen in one app.