33. An SEI teacher who teaches algebra and geometry classes that include English learners regularly invites students during problem-solving activities to use class supplies, such as grid paper, algebra tiles and blocks, algebra expressions and equations dominoes, geometric foam shapes, geoboards, circle and angle protractors, and graphic organizer worksheets. To evaluate students' progress in achieving unit objectives, the teacher uses an ongoing informal system of assessment, in which the teacher asks students to "show the steps" they use in solving representative problems. The teacher encourages students to explain their work orally or in writing, through drawings and/or through any of the class supplies described. This type of systematic formative assessment is particularly sensitive to the needs of English learners primarily because it: