Complex sentence: In 1969, it was announced that enrollment had plummeted and that there was a lack of Sisters to teach at the school; therefore, no new students would be admitted, and the current enrollment would be phased out.
Split into simpler sentences: In 1969, the announcement was made that enrollment had plummeted and there was a lack of Sisters to teach at the school. No new students would be admitted, and the current enrollment would be phased out.