The coach is the key. His parents passed away when he was young and he was brought up by his grandmother. He was a monk for about 10 years. He taught them how to meditate constantly even during training when the kids couldn't control their temper. This crisis puts the kids into the test, proved the power of meditation and team spirit.
This cave was not new to them and one of the kids didn't go because he didn't have his bike with him after soccer training. Some kids did inform the parents about it too.
It was the birthday for one of the team members. To celebrate this day, the coach brought them to the cave(which was not the first time that they've been there), and they're supposed to race in to write their names at the first wall of the cave. Then heavy rain fell and water started flooding in when they tried to return. To survive, the only way is to go deeper in to the higher platform.