The class three groups of order $p^9$ with exponent $p$
We give a complete list of the class two groups with exponent $p$ and order dividing $p^8$. For each group in the list we compute the number of immediate descendants of order $p^9$ with exponent $p$. In each case the number of descendants is PORC, and so the total number of class three groups of order $p^9$ with exponent $p$ is PORC. Nevertheless, there are groups of order $p^8$ with exponent $p$ which have a non-PORC number of class three descendants of order $p^9$ with exponent $p$.