This WebQuest would work best for any learner who just finished studying the Civil War. This will give them the appropriate background knowledge to complete the tasks proficiently. This WebQuest deals with a middle school audience (grades 6-8), because they must be mature enough to deal with issues like assassination. Although it is probably more fitting for audiences of 7th and 8th graders, it will work just fine with 6th graders.
However it is important to realize that some students not born in the United States, might not know the story of Lincoln's assassination. They may not be familiar with John Wilkes Booth at all so it may be helpful to give these students these helpful links:
Also please note that the WebQuest includes a drawing activity for those students who struggle with reading, and writing. :)