Using item response theory, this study explores whether student survey and classroom observation items can be calibrated onto a common metric of teaching quality. The data comprises 269 lessons of 141 teachers that were scored on the International Comparative Analysis of Learning and Teaching (ICALT) observation instrument and the My Teacher student survey. Using Rasch model concurrent calibration, items from both instruments were calibrated onto a common one-dimensional metric of teaching quality. Most items were found to fit the model. Challenges pertain mainly to items measuring teaching students learning strategies and differentiation. Explanations for these difficulties are discussed.