Solely the student's work with no outside help from any other person.
The student may consult with another person or persons. This person may be a parent, teacher, or other student. The written work is still crafted by the individual and is therefore distinctly different from any other student's version. The student must cite the resources used in consultation on the assignment.
A group of students works together on a problem or task to produce an answer/product.
Only acceptable when properly attributed. Copying independent work is never acceptable.