End marks ( . ? !) are used to designate a sentence, including grammatical complete sentences, purposeful fragments, questions, and interjections. [EDIT]
(3.P) The period is used to end sentences that are statements (not questions) and to designate abbreviations. A few important conventions are related to the placement of periods, noted in the examples. The final period comes after documentation in parentheses (see the first example), and the final period remains inside a closing quote mark (see the second example).
In “Public School 65, Down on the Lower East Side,” LaBrant (1998) recalls working with PS 65 from 1942 until 1953. The school, over fifty years ago, struggled: “The school was two years below the norm in reading, according to the latest all-city testing” (p. 7).
A series of extensive research reports on poverty and education in the UK paint an even more vivid picture of the impact of social realities on student achievement along with the probability that schools are unlikely to erase the impact poverty has on student achievement (Joseph Rowntree Foundation, 2007): “Just 14 percent of variation in individuals' performance is accounted for by school quality. Most variation is explained by other factors, underlining the need to look at the range of children's experiences, inside and outside school, when seeking to raise achievement.”
(3.QM) A question mark ends a question. Note the placement of question marks with the content of quoted material.
“Let’s not play these kids cheap; let’s find out what they have,” Ellison countered. “What do they have that is a strength?” (p. 548).
Why build a bridge to something that is broken, something that is lacking?
Ellison asked his audience to consider the positive qualities of failing students. (No question mark is the sentence is a statement about asking a question.)
(3.EP) An exclamation point denotes excitement, shouting, or an interjection. Writers are cautioned to avoid excessive use of exclamation points, except in dialogue that reflects excitement or shouting.