Find several objects to use for counting that are the same, such as paper clips, small rocks or craft sticks. Before working with preschoolers, count out 10 of each item and place in a small container.
Have the preschoolers count the objects in each container and then discuss how to add the 10 items to the next group of items to create the bigger number. Ten items plus an additional 10 create 20. Ten items added to 20 make 30.
Allow the preschoolers to practice counting the objects without help.
Practice counting while clapping and jumping to solidify learning counting by 10s. Before beginning to jump, clap and count, and discuss the numbers in 10s together. Start with 10, and then continue to 20, 30, 40, 50, 60, 70, 80, 90 then 100. Discuss how the numbers are similar to counting to 10, but slightly different.
Have the preschoolers jump and clap while chanting the tens from 10 to 100. Continue jumping, clapping and chanting until the preschoolers are able to chant without prompting.