URGENT! Anyone try interviewing in GSIS

My son will have an interview tomorrow at GSIS for getting into K1 this coming september. I worried that he'll fail since he's v. shy and doesn't talk much in front of stranger. At home, he only talks english with the helper and I'm not sure whether he knows what's mean by English!
Do anyone know how they'll test Since They request at least one of the parents have to be there too.