Only if the parents donated the money to a 501(c)(3) tax-exempt charity is there any tax exemption. The funds would have had to be used by the charity, for example, to purchase building supplies to build the school, food to be prepared in the soup kitchen for the hungry/homeless. Paying your own child's expenses while they do volunteer work is NOT deductible, nor is it tax-exempt.
It went for their child's accommodation, food, etc, not to the charity.