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!
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 PsycINFO or ERIC.
If you need ideas, a search like the following 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 PsycINFO you can limit your search by date and to journal articles using the links to the left of your search results.