It doesn't make sense. The period ends the sentence, not the phrase.
I'm with you, A-L.
I refuse to do anything that doesn't make sense regardless of the convention, unless I am likely to suffer some conspicuous penalty for it [like receiving a scornful arrow and surly red asterisk on an otherwise unblemished piece of work].
If you had committed an error not so conspicuously disrespectful of authority [in particular, her authority], your teacher's censure would have been far less emotive, AnimiaL. [One can forgive sins of ignorance or neglect, but not sins of presumption.]
It's my guess that your teacher has perceived an independent streak in you, AnimiaL, which she believes it is her solemn duty to expunge for the betterment of mankind.
Your teacher wants to bring you, not your period, to heel, AnimiaL.
Don't let her streak you out. But don't lose any marks over it either. :)
That independent streak will mark you as a leader in the future, AnimiaL -- whatever marks it may cost you nowadays in the classroom.
