In 1900, the BM Union High School was established in Sonakanda Mauza, Narayanganj district with government aid. The school was named after the Bandar and Madanganj (BM) Union and was established by the zamindar of the port Hari Mohan Sen and other nobles of the Union. However, the school building was burned down in 1921, possibly due to opposition to English education and leadership. Since it was not considered safe to rebuild the school at the original site, a new location was chosen. The preferred site was a piece of land owned by Datatrai and was donated by the zamindar of the port and other nobles. The words "School was established on our courtesy land" were inscribed on the school building in memory of the donors. The school library was established by one of the donors, Digendra Mohan Sen Roy, in his own name. The school was re-established in 1922 and received permanent affiliation with Calcutta University before 1931. The first school building was inaugurated in January of 1931. In 1947, the school was recognized by Dhaka University and later by the Dhaka Board of Secondary and Higher Secondary Education. From 2005 to 2016, the governing body purchased additional land. In 2013, a college branch was added to the school and was named the B.M. Union School and College. The college received permission to teach from the Ministry of Education in the 2013-2014 academic year. In 2018, the governing body purchased land on the east side of the Bandar Police Outpost road for the primary branch. In 2020, the single storey building was expanded to four floors. The governing body has also purchased land for the needs of the school over the years.