Varying the types of assessment you use in the classroom will help cater to the students' diverse abilities. For example, you could assign a multiple choice quiz or test to the students. Utilize performance assessment by asking the students to create different fractions out of manipulatives while you look on and evaluate their abilities. Employ criterion-referenced tests where students are judged on their abilities to master a predetermined set of objectives, not on how well they do as compared to the rest of the class.
Be sure that the tools you use are appropriate for the grade and ability of the students. In the earlier grades, introduce the students to manipulatives so that they learn the real life implications of fractions. A comprehensive examination of all fraction material would be more suitable for a middle school student who has been working with fractions for years. If the students have developed writing skills, ask them to write word problems or explain a particular fraction.
The frequency of assessment depends upon the type that you are using. For example, give students a short quiz after they finish one particular topic of fractions and an examination after the entire chapter. However, assess their learning on a daily basis by observing them during group work and individual assignments, as well as by asking them questions during lecture.
Grading can occur in the form of numbers and letters. However, you could also keep a journal of each student's progress and note how the student has done over the course of a semester or a year. Rubrics are another effective method for grading. For example, if you assign students a project on fractions, you would give them one grade for how well they incorporated fractions into the project and another for how well they presented the information to the class. Give them all the individual scores separately or tally them up for a final score.