Complex sentence: In 1898 and 1903, respectively, residents from the oil town of Olinda and the scattered oil camps that would become Brea created their own K-8 school districts, but it still would take more than two decades for a high school to come to town.
Split into simpler sentences: In 1898 and 1903, respectively, residents of the oil town of Olinda and of the oil camps that would become Brea created their own K-8 school districts. It would still take more than two decades for a high school to come to town.