一般现在时：He studys at Greenland Middle school.
现在进行时：He is studying at Greenland Middle school.
现在完成时：He has studied at Greenland Middle school.
一般过去时：He studied at Greenland Middle school.
一般将来时：He will be study at Greenland Middle school.
我想你写的文章应该只是介绍“他在格陵兰岛中学上学”,那么用一般现在时就行了.