Complex sentence: In 1987, he became the Director of Developmental Pediatrics at the school's Department of Pediatrics; in 1989, he became the Medical Director of the Waisman Center's Clinical Services Unit.
Split into simpler sentences: In 1987, he became the Director of Developmental Pediatrics at the school's Department of Pediatrics. And in 1989, he became the Medical Director of the Waisman Center's Clinical Services Unit.