We present a framework for articulating learning difficulties in computer science (CS) based on the socio-cultural theoretical idea that learning means entering a culture. In school, teachers and students participate in two cultures simultaneously: (1) school and (2) the domain studied. CS students are members of a third culture, computer users and thus, in CS lessons, three cultural viewpoints are employed simultaneously, which might recast students' understanding of CS with ungenuine- CS elements. The power of this framework was demonstrated in a three-phase investigation into difficulties regarding correctness using questionnaires. The first two phases revealed how both school and the user's culture nurture students' misconceptions of correctness, which contribute to students' inadequate work habits. The third phase exposed teachers' dual viewpoint on a programming activity, which students can misinterpret as agreement with their (mis)understanding of the concept. Copyrigtht 2008 ACM.