Academies in the UK are independent state schools which are directly funded by central government and enjoy high level of autonomy. They are a fast growing school type in recent years, aiming at enhancing school performance. The predecessors of academies are City Technology Colleges built under the Conservative government in the 1980s. In 2002, some of the City Technology Colleges are transformed into academies and ignited the steady growth of this new school type by the New Labour government. The Coalition government passed Academies Bill in 2010 and accelerated the growth. The present study analyzes documents from Department for Education of the UK and the UK Parliament and other related literature to explore the administrative system of academies and their performances. The findings suggest that school autonomy has positive meaning to educators and preliminary effect on enhancing students' performance. The comprehensive and long-term effect of academy school system, however, remains vague. Conclusions and recommendations are proposed according to the findings.