The scene takes place during World War II Poland in 1944, where we first meet the young Eric Lensherr inside a Nazi concentration camp, and where he first discovers his ability to create magnetic fields. The first steps on Lensherr's path to becoming Magneto. Matthew Vaughn is recreating the scene shot-for-shot, at least up to a certain point, where he will then add his own twist on the iconic moment.
The site also reports that Son of Rambow's Bill Milner will be portraying the young Leshnerr/Magneto in this particular scene. They wouldn't reveal the twists involved, but they did say Matthew Vaughn is paying close attention to detail in the scene, with video reference of the first scene available for cast and crew members to recreate it in exquisite detail.