Massive Open Online Courses appear to have high attrition rates, involve students in peer-assessment with patriotic bias and promote education for already educated people. This paper suggests a formative assessment model which takes into consideration these issues. Specifically, this paper focuses on the assessment of open-format questions in Massive Open Online Courses. It describes the current assessment methods in Massive Open Online Courses and it argues that self-assessment should be the only way of formative assessment for the essays of xMOOCs and replace the peer-assessment.