Abstract: The study was carried out in Bo City, Southern Province - Republic of Sierra Leone. Bo city is the third largest city in Sierra Leone by population (after Freetown and Kenema) and the largest city in the Southern Province. Bo is the capital and administrative centre of the District. Bo is an urban centre and lies approximately 160 miles (250 km) east south-east of Freetown and about 44 miles to Kenema. Bo is the leading financial, educational and economic centre of Southern Sierra Leone. Bo was previously the second largest city in Sierra Leone by population, the city is the primary home of Njala University, the second largest university in Sierra Leone, after the Fourah Bay College. Bo is also home to the Bo Government Secondary School, commonly known as Bo School, which is one of the biggest and most prominent secondary schools in West Africa. The school has a history of producing some of Sierra Leone's most gifted and outstanding students. The study was initiated to investigate the Effect of Leadership Styles on School Administration in Selected Secondary Schools in Bo City. The study hypothesised that there is a relationship between administrators’ leadership styles and school effectiveness for the smooth running of the school which enhances commitment of teachers towards quality education. Most important of what the study revealed was that, many teachers have been elevated to leadership positions (administrators) without much formal administrative training leading to ineffectiveness and mismanagement of schools, hence poor students’ performance and disappointing results. It was also revealed that many schools that were once effective in academic performance have lowered their standards due to poor leadership while some have greatly improved through effective leadership. The effectiveness of schools has continued to dwindle despite the fact that the schools ............................