Academic, public, and many "special" libraries (e.g. corporate, pharmaceutical, medical, law, etc.) generally require that you have a Masters in Library Science (or equivalent content--titles vary) from a graduate program that has been accredited by the American Library Association. There are somewhat less than 60 of these in the US and Canada. States set requirements for school librarians and these requirements may be met with the appropriate combination of courses in education (and certification as a teacher) and courses in library & information science-- resulting in certification as a school library media specialist. The formal degree may not be required though most students do it because it allows a greater degree of flexibility. My impression is that private and parochial K-12 schools do not have to meet state certification requirements for school librarians in PA but states differ in requirements.
The undergrad degree can vary widely and I have had students with degrees in law, medicine, pharmacology, nursing, and a range of PhD programs.
The "I" in this case is a faculty member/Associate Dean in the College of Information Science & Technology at Drexel University in Philadelphia -- we house the second oldest library science program in NA, continuously accredited since the 1920s and available as a totally online program as well as on-campus. For a full range of accredited programs and other information about becoming a librarian, you might look at:
(1) the website of the Association for Library and Information Science Education-- the page that lists all of the ALA accredited program websites
http://www.alise.org/membership/instmembers.shtml(2) the website of the American Library Association page on library careers
http://www.ala.org/ala/education/educationcareers.htmIf I can give you any other information about the range of opportunities for information professionals with the skills and knowledge imparted by the MLS, I'll be happy to do so.
Kate McCain