The Boys from Datra by Jan Weeks

Eleven-year-old Meg definitely does not want to be left in Australia with her aunt and uncle, even if they are nice people, while her father goes to the South Pole to make a documentary about endangered animals. It’s so unfair, particularly when he’s always taken her in the past when he visited other countries. But before, she always had Anna to take care of her and tutor her at home. To make things even worse, she now has to go to public school. It doesn’t take Meg long to realize that there’s something weird about Peter, the boy next door. He quotes statistics like a parrot, leading Meg to believe he has a computer where his brain should be! When she sees Peter sneaking out of his bedroom to disappear into the bush behind his house in the middle of the night, she follows him to discover where he goes. If she had known what was hidden in that clearing in the bush, perhaps she might not have been so eager to discover his secret.