Introduction It should be noted that American schools have undergone significant structural changes in recent decades. The changes concerned increased not only ethnic and cultural diversity but also knowledge assessment systems. A widely used technology for obtaining school evaluations is testing, active work during the lesson, or homework. However, it is not difficult to understand that a teacher’s score does not always reflect a student’s actual knowledge qualitatively and objectively. The most important criteria for evaluation assessments are validity and reliability. This essay aims to discuss the application of the concept of valid and reliable results of a student’s educational process in the context of English language learning. Credibility and Reliability of Evaluation The modern school follows the path of active implementation of data subject to statistical processing to find an objective system of evaluation, models of teacher-student interaction, and drafting quality tasks. In other words, schools tend to minimize the subjective human factor so that the student can know that the knowledge and scores they receive are actual (Cucina et al., 2016). Thus, the study of English teaching — particularly for students with limited knowledge (ELL) — becomes relevant because the subject plays a vital role in a student’s life. Reliability When a student receives a grade for a quiz or assignment completed, they want to make sure that the assessment is not affected by contextual factors — the teacher’s or student’s mood, the amount of work to be checked, or an imperfect grading system. In other words, the student wants to ensure that the assessments they receive meet the criteria for validity. This means that the test or assignment does indeed measure what they intend to measure (“Importance of validity and reliability,” 2020). Exaggerating, one could give the example that it makes no sense to give pupils a passage in English for public reading if the text is incredibly shallow and imperceptible to the eye — this is how the teacher intends to check not so much the student’s actual knowledge but rather their vision. In order to create a quality assessment system, the teacher must be based on validity. In particular, it is necessary to verify that the tests developed, namely, the points, questions, and expected answers, are relevant to the English language and aim to test specific subject knowledge (Amrein-Beardsley & Geiger, 2020). Moreover, education specialists consider it an ideal strategy to mix different approaches to obtaining reliable data (Ghazali, 2016). This strategy provides a one-size-fits-all model for checking teachers’ intentions when preparing assignments and assigning scores. The reliability of the data received is considered to be an equally important evaluation criterion. Reliability corresponds to the degree of consistency and accuracy of the results of the educational process (“Reliability and validity,” n.d.). Existing strategies, such as Test-Retest, should be used to gain confidence in the reliability of the evaluation system (Shillingburg, 2016). If a student who writes a test fails, they should understand that the same grade will be achieved when they write it again. In other words, the importance of reliability in the assessment o