As all long time members of Wizarding Britain know, the entrance to platform 9¾ is located inside one of the pillars in Kings Cross station between platforms 9 and 10. More informed members know the spell that causes people to move from the pillar in question to the Hogwarts station deals primarily with distance. You see, the train is not located at the station at all, but a few miles away. The spell is similar to what people assume a magical 'Gate' would be. It moves you from one place, to the other.
The scholarly gentlemen of academia would be able to tell you why the gate behaves this way. They would also stress that you should not attempt to change the gate in any way, for gates are fickle things and have been known to change their locations, shapes, and even the times they are open with only the slightest external pressures. They would also stress to only have three people pass through at a time. The magics don't like more than that they said.
This would be the case with one Harry Potter, along with a few other assorted magicals going to school that year. It had started when he and his friend, one Ronald Weasly, attempted to pass through the barrier with their luggage and were rebuffed. It seemed they were not to get in at that time, for little did they know, a house elf by the name of Dobby was nearby and had taken it upon himself to keep Harry from getting to the school that year.
Now enter out mischief maker, Draco Malfoy. Him, and his parents were also running a little late, something about the floo powder getting replaced with ash or something. As they arrived, Draco witnessed the two boys ram themselves into the barrier. He promptly started laughing, pointing his finger at them comically. This aggravated the two boys, causing them to start bickering loudly with Draco who, while with his parents went into the same routine he always did with Harry and Ron. Boys being boys the words quickly turned to blows. Harry and Draco were at each others throats near the barrier trying their hardest to beat the other to a bloody pulp. Ron was watching from a few feet away about to join in.
Due to this commotion none noticed two girls nearing the barrier, Daphne Greengrass, long known as the Ice Queen of Slytherin at school, and Luna Lovegood, a soon to be first year. Daphne looked at the two boys in distant briefly then moved to go through the barrier regardless of their brawl. Luna, her head tucked safely in her magazine, didn't even notice the two boys fighting other than to dodge around them on the way to the divider.
That's when it happened. As the two girls reached the barrier Draco charged Harry, pushing him towards the wall. As the four of them hit the gate, something strange happened. The gate, already trying to work under the hindrance of Dobby's magic, suddenly tried to send all four children through at the same time.
There was no flash when they were pulled through. One moment they were there, and the next they weren't. Even the four children's luggage was taken.