Prepare a basic worksheet with simple addition facts. Use only single-digit numbers. For example, 3+2=? Start with smaller numbers that total less than 10. Include some larger numbers near the end of the worksheet, such as 9+3=?
Prepare a similar worksheet for subtraction. Use numbers smaller than 10. For example, 8-3=? and 9-5=?
Have the students work on the worksheets individually in class. Make note of which students complete the worksheets more quickly than their peers. Allow the slower students to have more time if required. Make note of which students take longer than most other students.
Collect the worksheets and correct them. Prepare similar worksheets with more challenging addition and subtraction facts if most of the students complete the first worksheet quickly and accurately.
Write some addition and subtraction facts on the board. Have students provide the answers orally or have them write the answers on the board while the other students check if the answers are correct.
Work individually with the slower students who appear to be having difficulty. Provide additional addition and subtraction facts for them to demonstrate their level of mastery.
Test the weaker students and drill them on simple basic number combinations, starting with small numbers less than 5. Retest them after several practice sessions to determine if there has been any progress.