Research has shown that emotions play a significant role in the learning process and academic achievement. However, the fact that measurement of emotions during or after instruction usually requires written responses on lengthy research instruments has been given as a reason why researchers have tended to avoid research on this topic in classrooms. Consequently, we developed a short Likert-scale instrument which used only three items within the three factors of interest, well-being and boredom to measure adolescent emotions during instruction in science education. We present four different studies in four populations to assess the validity of the scale. In order to determine the reliability and validity of the instrument, it was administered to pupils across a range of grades (grades 6-12) after being taught standardised lessons by 14 teachers in south-western Germany. The data generated were analysed statistically in terms of their reliability and validity. As the three independent factors (interest, well-being and boredom) had been derived from theoretical constructs, confirmatory factor analysis was applied. In a second study based on pupils from different age groups, grades and school subjects, we found different scores according to age and subject, suggesting that the scale is sensitive to these parameters. A third study used two standardised educational programs in zoology and botany for 5th and 6th graders to assess the scale‘s sensitivity towards changes in emotions. Pupils rated the zoological topic as more interesting than the botanical topic, as less boring and they felt better. External validity was determined by correlating the data that was generated using our scale in a fourth study on University students with the data generated by an established measurement of motivation (the shortened German version of the KIM - ―Kurzskala zur Intrinsischen Motivation‖). The data generated suggest that the three factors cluster satisfactorily and that the instrument, which can be administered with minimum disruption of classroom time, is both reliable and valid.