The most effective conclusion to Chelsea's essay is:
"As shown, homework is not a necessary factor in student academic success. Students who are given hours of homework each night struggle later in life with finding balance between work and their personal lives. In addition, free time is an important part of the teen years, and students miss out on an important part of their adolescent development due to homework."
This conclusion effectively summarizes the main points of the argument and maintains a formal and respectful tone consistent with an academic essay.