If you live in Seagrove, you will be zoned for Bay Elementary School, which is just 4 miles up 395 (and very close by for SoWal standards). It is a wonderful small school that has the feel of a private school with a lot of parent involvement. All of the FCAT scores are not out yet, but the 3rd grade at Bay had the highest overall test scores of any 3rd grade in the county. Bay's first year as a K-5 school was last year and it received an "A+" rating. Butler is also a good school, but you will not be zoned for Butler (but your kids can also go there).
South Walton Montessori Academy has moved to Point Washington, and is near Bay Elementary. We've had personal experience with this school and enjoyed it, but couldn't afford it with 3 kids in the school.
For middle school, a beautiful new middle school (Emerald Coast) is planned for the intersection of HWY 98 and HWY 395. The school is scheduled to open in 2 years. Emerald Coast is currently located behind Butler Elem. in an addition that will become part of Butler once the new school is built. Another option is Seaside Neighborhood School which is a charter middle school that is one of the top 10 middle schools in Florida. Enrollment is by lottery--some years chances are good, some years not.
South Walton High School is new and small. Overall it is a good school with an "A" rating.
There are a few other private schools in outlying communities. However, I think you'll be satisfied with the school choices in South Walton. For a small rural area, many families are very well educated and have high expectations for quality education.