Zero and the counting numbers
When children count backwards from 10, some learn to finish the backward count with “zero” and others with “blast off”. Although there is value in counting down from 10 to 0, a problem arises when some children begin a forward count from zero. In developing a one-to-one match between objects and counting words, children can allocate the word “zero” to the first object counted. For this reason, the descriptions of the levels of the counting words do not include zero.