Parental control of the child's actions on the Internet is undoubtedly necessary, but he does not guarantee the result at all. On the one hand, if a child, especially a sufficiently conscious age, or even more so a teenager decides to get some information, the presence of restrictors on his devices will not change anything. There is always a friend's smartphone or neighbor's computer, and traditional channels of information transmission have not gone away - conversations with peers. On the other hand, parental control helps to protect children from accidental access to unnecessary information.
One can argue long about the age and what the child should know, but the ease with which the Internet carries us, often in addition to will, to resources with contentious content, still stimulates parents and guardians to take certain actions.
The ability to determine the boundaries for which a child does not need to go online is the second aspect of parental control. For some it will be sex and violence in any manifestation (then, however, it will be necessary to avoid even billboards in the city), someone will want to shield the child from information about the existence of drugs and abortions. The more flexible the system that allows you to restrict access to content, the better.
Parental control can be divided into different groups depending on the platform on which they are used (computer, smartphone, tablet), and the "depth" of the impact on the work on the web. The most soft can be considered various settings of search engines and browsers, while the hard-coded filtering on your Internet router, most likely, the child will not be able to get around.
а) Они хотели видеть зонтик мисс болтовни
б) Они любили работать в классе