In a recent decision, the Appeals court held that a father could not unilaterally stop child support and educational expenses for a child over 18 without filing a modification with the court. In a case decided on August 16th called Barnes v. Devlin the court held the agreement had been incorporated into the judgment and the father had assented to the support order. The father argued that the conditions of Mass General Law ch. 208 s. 28 were not met, and he was not obliged to pay the support since the stipulations were null and void, in contravention of the statute. The father contended that the conditions of the statute : " provided said child is " domiciled in the home of a parent, and is  principally dependent upon said parent for maintenance." were not proved. The judge declined to address the issue, and ordered the father be held in civil contempt.
See our pages on Child Support over 18 and Modifications.