Complex sentence: The school building stood until the early 1990s, when its roof blew off in strong winds, and its walls were taken down to strengthen the wooden bridge constructed by the Royal Marines in 1980 crossing the Daill River to the north west of Achiemore.
Split into simpler sentences: The school building stood until the early 1990s, when its roof blew off in strong winds, and its walls were taken down. A wooden bridge was constructed by the Royal Marines in 1980, crossing the Daill River to the north west of Achiemore.