The qualifying criteria on their website say that a score of +3 SD on a IQ test qualifies students for admission, and that students with scores higher than 2SD are assessed to determine if they qualify. Sounds to me like they're looking for HG+ kids.

Given that this school doesn't charge tuition, I would suggest that you attend an open house. You'll get more information by visiting and from talking to parents of current students than you're likely to get here.