It really depends on the child. I have had some, as young as three, who were able to repeat targeted words of importance to them until they mastered them. Others have been resistant to repeated practice, and we play while I model a variety of fun sounds (vocal play). The child often imitates me, I imitate them, and pretty soon the kiddo is imitating a variety of sounds which we can shape into words. Every child is different, and I follow their lead regarding interests and ability/willingness to imitate. I like to send home little books and activities that parents can repeat to help with generalization of skills, as well as getting important words (family names, toys, pets) from families to use in therapy. Your priorities and your child's comfort are important to me.