Complex sentence: The first school had been opened in 1683 but education in the town began in earnest in 1859 with the opening of a seminary for the Dutch Reformed Church and a gymnasium which known as "het Stellenbossche Gymnasium" was established in 1866.
Split into simpler sentences: The first school had been opened in 1683 but education in the town began in earnest in 1859 with the opening of a seminary for the Dutch Reformed Church. A gymnasium which was known as "het Stellenbossche Gymnasium" was established in 1866.