Counting aloud is not the same as counting objects
A child may recite one to ten but count an object twice. Put five objects in a row and move each one while counting. Check that the final number describes the whole set.
Choose objects that are easy to move. Small buttons and blocks can be choking hazards; supervise and keep them away from younger siblings.
Split five into two groups
Move two objects away from a set of five and count the three remaining. Join them again while saying that two and three make five. Try one and four, then zero and five.
Show zero with an empty plate beside a plate holding five objects. The total stays five even though one group is empty. Show the situation before introducing its written symbol.
Hide a group to make ten
Once five feels comfortable, use ten objects. Leave six visible and cover four with a hand or paper. Ask how many are hidden, then uncover and count them to check.
If the answer is wrong, reveal all ten and move six into a separate group. Seeing the remaining group is often a clearer next step than immediately asking for subtraction in the head.
Connect the objects to the worksheet
Match the written question to the groups of objects before filling the blank. A reversed written digit does not necessarily mean the child misunderstood the quantity; check the two skills separately.
For a two-digit number such as 21, show two bundles of ten and one single object. Connect the bundles to the tens digit and the single object to the ones digit.