The focus of this review paper is on the assessment of English Language Learners (ELLs) and the ways in which the language gap negatively influences ELLs in classroom assessments. The research body provides an outline of differentiated instruction and assessment highlighting the primary obstacles that hinder ELLs from achieving success in various classroom assessments. It explains the importance of addressing the language gap due to its wide-reaching impact. Additionally, it underscores the significance of differentiating instruction and scaffolding assessment to accommodate language, culture, and previous educational experience. This consideration is especially crucial as assessment results may be biased or inaccurate if these factors are not taken into account. Finally, the paper discusses several strategies that teachers can implement to enhance their instruction and assessment methods.