To simply put it, very important.

In a study conducted by Sommers, R., et. al. (1967), a total of 288 children in a suburban school system received articulation treatment from a team of 20 speech therapists. Before and after an eight-and-a-half-month therapy period, articulation tests were performed to see if the patient had improved. The authors of the journal paper came to the conclusion that the factors of grade level and degree of defectiveness did not interact to impact the success of treatment. Furthermore, stimulability was shown to be in the expected direction, with patients with low stimulability ratings showing considerable improvement as a consequence of speech correction when compared to those with excellent stimulability scores. It is also clear that, regardless of their stimulability ratings, those who underwent speech therapy showed considerable improvement as compared to those who did not get treatment.

Speech therapy is vital for children's intelligibility. It has a positive influence on their ability to communicate verbally. This research stated that regardless of the severity of their speech problems, speech therapy has been shown to be successful for children in kindergarten, first, and second grades. The findings alone should not be considered for determining whether or not these children should be engaged in a correctional program; instead, additional critical characteristics should be considered.