Complex sentence: Nichkhun went to private school from pre-school all the way up to 7 th grade in Thailand and went to a school in New Zealand for one and a half year then moved back to the United States and finished his middle and high school years there.
Split into simpler sentences: Nichkhun went to private school from pre-school to 7 th grade in Thailand and then went to a school in New Zealand for one and a half year. He then moved back to the United States and finished middle and high school years there.