Government documents and government websites are generally consideredauthoritative, credible sources of information. Many are scholarly, and some are even peer-reviewed!
But, not allgov docs are scholarly or peer-reviewed. Government agencies produce a wide range of publications, for different purposes. Depending upon your research assignment's instructions, some documents may be a better fit than others.
For example: skim this page of publications about air quality from the U.S. Environmental Protection Agency. You'll notice that some of them are intended to educate the general public, while others are technical reports (written for environmental professionals). While the former are great for background information and/or study help, the latter are the kinds of publications that would be considered scholarly.
When in doubt, remember that scholarly publications:
Are written for researchers, scholars or professionals in the field. These will usually be somewhat lengthy, and will cover the topic in detail (with plenty of technical language).