A national curriculum for the study of computing became compulsory in English secondary schools in September 2014, replacing the study of information and communications technology with computer science (CS). This posed difficulties for teachers and students who did not have knowledge or experience of programming. This study was designed to investigate and gain a critical understanding of the teaching of computer programming (CP) at Key Stage 4 (KS4; year 10-11) of the CS curriculum, including assessing the impact of learning CP and students' perceptions of CS and their overall performance in the subject. Furthermore, the study investigated the measures to improve the teaching of CP and the factors that have an impact on the effective teaching of the CP curriculum. The study sample comprised 300 students. The findings indicate that the main difficulties the study found that the issues faced by students learning programming include a lack of time, the perceptions that it is a 'difficult' subject and students' insufficient understanding of programming. The findings also suggest that schools have made efforts to overcome these challenges and are willing to adopt programming as a subject and to help, encourage, develop and improve students' ability to learn programming; however, the results indicate that it is essential that schools address the shortage of teaching staff with specialised knowledge of CP. This study revealed that three factors can help to overcome the difficulties where the three factors are for students (perceptions towards learning and teaching programming, benefits, and support). The findings of this study will be useful for students who are learning programming in secondary schools.