In a longitudinal study of a group of students from the natural science program at upper secondary school, a survey is made of which factors facilitate or obstruct their learning of algebra. Both cognitive and affective factors are considered. The five main factors that influence the teaching and learning of algebra are: pre-knowledge, concept development, instruction, time for learning and interest, attitudes and feelings. In a special part advice for teaching is given and a model for support of lower-achieving stunts is presented.