Dr. Rif`at Fawzi, former professor of Shari`ah at Cairo Univ. , states:

“It is permissible, as far as Islamic Shari`ah is concerned, to offer the whole prayer with an audible voice to help children learn how to offer prayer. This is permissible even when it is a silent prayer like Zuhr as you have a good Shar`i objective and children most probably learn prayer through this way.