"बाल" is a mass noun, referring to many units seen as one whole. A mass noun can take both singular or plural verb. For instance, when the noun is viewed as one whole "hair" "news" and "rice" , it takes a singular verb. However, when a mass noun is referring to the many members within that noun (for example, the word "community") then the verb can be plural. "The community are not responsible...." meaning the community 'members' are not responsible. Here, "community" can also be used in the singular sense as one whole body, "the community finds fault with..."