It really depends on what you need to modify, and why.
Let's get some more information:
Is this strictly a parent request?
Is this child new to your school? If not, have you investigated his/her history with previous teachers?
Does your school have some sort of "Student Study Team" provisions to meet with other teachers, parents, etc. to address problems? If so, have you had a meeting?
Does the child have an IEP or qualify for any special services?
What exactly do you need to modify, and why?