My problem with the slang is that I lived that era and it is WRONG. It is not only wrong in actual vocabulary, it is wrong in how it is used. Teenagers of that date who used arcane vocabulary were invariably diglossal; when they wanted to confuse Authority they used slang, but when they needed to communicate with other people (including, for example, parents, aunts and uncles) they were perfectly capable of producing standard usage. In particular, if in a one-to-one conversation with an outsider, they wouldn't use slang because there would be a risk of the outsider learning the meaning of the slang terms, which was something that had above all to be avoided.