80% of a student's grade is from summative assessments
20% of a student's grade is from formative assessments
Formative assessments are assessments FOR learning. These are daily assignments and quizzes that help inform the teacher if the students are developing mastery of a concept. Since students ARE NOT expected to show mastery at the time of a formative assessment, it carries less weight on their grade.
Summative assessments are assessments OF learning. These are assessments given at the conclusion of a unit of study that includes a set of skills and standards. Since students ARE expected to demonstrate mastery at the time of a summative assessment, it carries most of the weight of their grade.