The objective of this study is to explore the potential for developing IRT-based working memory scales for assessing specific working memory components in children (8-13 years). These working memory scales should measure cognitive abilities reliably in the upper range of ability distribution as well as in the normal range, and provide a much-needed, reliable, and valid test for assessing high intellectual abilities in children. Six computer-assisted working memory tasks were administered to 172 children from regular schools and to 202 children from special schools and other institutions for the gifted. A factor analysis revealed a two-factor structure and the existence of a verbal-numerical and a visuo-spatial working memory scale. Classical item analysis and IRT analysis yielded good psychometric properties for both scales and revealed that the scales are appropriate for measuring high cognitive abilities. Both scales showed substantial and differential power for the explanation of variance in school achievement.