Complex sentence: The school leaving age was raised to 14 in 1901, and although plans to raise it to 15 in the 1940s were never ratified, increasing numbers stayed on beyond elementary education and it was eventually raised to 16 in 1973.
Split into simpler sentences: The school leaving age was raised to 14 in 1901. Plans to raise it to 15 in the 1940s were never ratified, but increasing numbers stayed on beyond elementary education and it was eventually raised to 16 in 1973.