This paper discusses Singapore education system as a whole including primary, secondary and high school cycles, and tries to examine the country status in PISA 2015. It also aims to reach various conclusions by examining science and mathematics curriculum, teaching strategies, teacher education of Singapore. The paper discusses the success of Singapore in PISA and tries to examine critical success factors behind such a success and examines challenges for Singapore education in PISA. All in all, Singapore has achieved and learnt lessons from its mistakes, created a newly designed and successful education system in international exams.