Cathedral Catholic is a three-year-old school that many have likened to a college-like campus, with many high-tech applications. The school was borne out of University High School next to USD. http://www.cathedralcatholic.org/
It’s on Del Mar Heights Rd., which can be a trek from Carlsbad in the morning, but worth considering. Pacific Ridge and Santa Fe Christian are also well thought of, as the comments above confirm.
Renting is a good idea to consider, to get comfortable with the neighborhoods. The chances of you finding a great house at a great price while out-of-town are pretty small.