Arno M said:
"Parents and school administrators and especially in the United States, local school boards. A teacher who allows their students free access to Wikipedia is a fool."
A similar question involves minors accessing it at home or in some public library that bans access to sexually explicit sites.
In my opinion, Public libraries should not permit unsupervised minors to use the internet unless their parents first, being properly informed as to the nature of the internet, knowingly and explicitly give the library permission to do so.