Educational effectiveness research focuses not only on cognitive output but also on affective student outcomes. Student wellbeing has to be addressed as an important output variable of the educational process. The focus in this study is on student wellbeing at the end of Grade 10 and its relationship to current achievement, and pre-measurements of student wellbeing and achievement. Student characteristics and motives for attending school are taken into account. Moreover, within classroom environment research, student perceptions of psychosocial characteristics within the classroom are considered as an important factor in the explanation of student wellbeing. Data from 429 students at 13 different secondary technical and vocational training schools in Flanders (Belgium) are used. The results indicated that pre-measurements of student wellbeing and achievement are positively related to student wellbeing at the end of Grade 10. No relationship was found between student wellbeing and achievement when both are measured at the end of Grade 10. Furthermore, students feel better when they perceive their teacher's interpersonal behaviour in the classroom as tolerant/authoritative and not as authoritarian.