Complex sentence: Allameh Helli No.3 High School is an education center that was established in 2008 and, at the time of its commencement, was the second NODET high school in the Iranian capital city of Tehran.
Split into simpler sentences: Allameh Helli No.3 High School is an education center that was established in 2008. It was the second NODET high school in the Iranian capital city of Tehran.