Halo effects in teacher judgments, can occur when the assessment of one aspect of a person's achievement is generalised to another aspect of achievement for that same person. We conducted an experimental study in which participants (N = 107) had to grade vignettes of the same student in two different subjects. The first vignette described either a weak, average, or strong performance, whereas the second vignette always described an average performance. Thereby, rich descriptions of achievement-relevant information were used, and the impact of influencing factors was reduced. The treatment condition emerged as a significant predictor of the grade given for the second vignette even after controlling for gender, status of the participants, and the gender of the student. The results suggest that participants' ratings can be manipulated to show halo bias. The results support the view that teacher education should raise awareness of possible sources of the halo effect.