The 120's chart is a great tool for practicing place value, expanded form, and addition facts. Additionally, when students place numbers on the 120's chart, they are learning to notice patterns between numbers. As students become faster in completing the chart they ‘level-up' to other math constraction.
In front of your students (they love this part), gently shake it so that some of the numbers fall out. Hang the hundreds chart back on the board/wall. Students can take turns putting the loose numbers back into their proper spots on the hundreds chart. you've found that creating small groups of students with similar abilities works out great, because they really work together to complete the task, and can more or less be left to complete the work without a lot of adult supervision. This is a great opportunity for students to use problem-solving strategies, and to learn about math patterns using their own reasoning skills.