Hi,
Marietta can fall under a couple of school districts. The City of Marietta has its own school district (Marietta School District), while the unincorporated areas are in the Cobb County School District (someone please correct me if I have that wrong...this is the way I understand it).
I do not have personal experience with the Marietta School Dist., but have heard it isn't very good. Hopefully someone else can offer info on that. Cobb County's school district is pretty huge, so parts of the district can be good, while others can be not so good. Do you know in what part of Marietta you might relocate?
Here are a few good websites for researching schools:
GreatSchools.net
Schools, High School, Public Schools, School District, Public High Schools - SchoolMatters
Here is Cobb County School District's website:
Cobb County School District Home Page
Here is the City of Marietta's School District website:
Marietta City Schools