Many students struggle with mathematics, in Norway a pressing concern is the decline in proficiency in high school, and the increased number in need of special education. Assessments of proficiency levels are traditionally done through norm- and criterion-referenced achievement tests, who will rarely detect students struggling or identify effective interventions. In a systematic replication of Lin and Kubina authors examined the relationship between component and composite frequency and accuracy; systematic variations were inclusion of multiple grade levels (5-9), assessing association between composite skills and component skills, and a second screening identifying natural levels and gain. Findings show that component frequency is associated with composite frequency and as such support the findings from Lin and Kubina, and also support the notion that basic skills are prerequisites of more complex skills. Natural level was overall below US students, as was natural gain.