The "research part" of this assignment:
"You will need to conduct a literature search and identify a research article that has been published since 2005 that discusses a common misperception related to autism....Students may not select the MMR vaccine or the gluten free diet as a topic."
For this topic, PsycINFO (with its psychology focus) will likely be your best choice. Though if you want to examine misconceptions related to autism as it's seen in the classroom, ERIC (the education index) would be better. Try both!
Description: PsycInfo is a key database in the field of psychology and related disciplines such as neuroscience, business, nursing, law, and education.
Coverage: 1887 to present with some content as far back as the 17th century
Sources: Indexes more than 2,400 peer-reviewed journals.
Subject Headings: Psychology, Education, Social Sciences
Material Types: Journal Articles, Dissertations, Theses
Description: ERIC EBSCOhost is a key database in the field of education, providing access to journal articles, ERIC documents, dissertations and other materials.
Coverage: 1907-present
Sources: Contains 2 million records with nearly 600,000 full-text, peer-reviewed articles.
Subject Headings: Education, English, Literature, Fine and Performing Arts
Primary Materials: Journal Articles, Documents, Government Documents, Books/e-books, Dissertation and Theses, Reference Entries, Reports, Grey Literature
You may have a misperception in mind already, from experience or from previous research you've done. Great! Go with it! Take your topic to a database like APA PsycInfo or ERIC.
If you need ideas, you could search using these terms, spread over two boxes:
A search like that could help you to identify articles which discuss the misperceptions related to autism, so you can choose a misperception for your focus.

You may find an article to discuss in your post using this method, or you may want to get more specific by focusing on a certain misconception.
Consider examining the references referred to in a research article for ideas of other titles to consult.
Notice that in ERIC and APA PsycInfo you can limit your search by date and to journal articles using the Filters options.
