Complex sentence: However, starting in the mid- 1960s and continuing until the early 1980s, SAT scores declined: the average verbal score dropped by about 50 points, and the average math score fell by about 30 points.
Split into simpler sentences: However, starting in the mid- 1960s and continuing until the early 1980s, SAT scores generally declined. The average verbal score dropped by about 50 points, and the average math score fell by about 30 points.