In the 18th century at the initiative of the King of Prussia Frederick William I a decision was made to reconstruct the school so that it had a neoclassical style. In 1805 the school was connected with the municipal middle school and Mariackie Royal Middle School was created.
Over the centuries, the building was reconstructed many times. When the Mariacki church was liquidated in 1830 a decision was made to build a new school building. It was designed by Scabell, and the construction works were completed in 1832. Two years later the town council funded organs for the school, and around the school chestnuts and maples were planted. The school library had approx. 30 thousand books and it was the best supplied library in the Pomerania Province.
Because the school was not big enough, they decided to build a new building, and when it was completed in 1869 at Mariacka Street a four-grade initial school was created, and then it was transformed into private apartments. Today there is the 9th Secondary School in the building.
Next to the school building there are remains after the Mariacki church – two spans of the cloister which connected the church with the houses of the professors.
There is a bronze board on the wall of the school with the following content: “On the 18th of May 1944 Polish soldiers of the 2nd Corps conquered Monte Cassino in the Battle of the Nations fighting for Rome. On the 40th anniversary of the battle to honour the victors the school received the following name: IX Liceum Ogólnokształcące Bohaterów Monte Cassino in Szczecin (The 9th Secondary School named after the Heroes of Monte Cassino). 18 May 1989.”
The building was included on the list of monuments of the province in January 1985.