本群组为非公开，您没有足够的权力访问?

When I visit 高中信息交流, it says "本群组为非公开，您没有足够的权力访问", so I registered but still cannot see it. When I click join link, I got "您已经加入了本群组, 请不要重复递交申请！". So I wonder why I still cannot view the info under 高中信息交流. I still see ""本群组为非公开，您没有足够的权力访问". How to join the group?