There are multiple sets of norms for when children typically grow out of using various phonological processes. This chart compares the different norms so you can make the best recommendation based on your students' needs.
The norms include:
First Years Chart from norms in Lowe, R.J. 2000
Table 3.1 Adapted from Articulation and Phonological Disorders (4th ed.) from norms by Bernthal & Bankson 1998
Table 3 citing Bowen 1998, Grunwell 1997
Figure 6.2 in Haynes 2004 citing Grunwell 1987