In Catholic schools, they do teach religion along with the regular academics, and in my personal experience, they’ve been a better learning environment than the public schools in the same area (I’ve taught in both Catholic and public schools). But please don’t get the idea that Catholic schools don’t have their share of problems from time to time. They have bullies, cliques, etc., but from what I’ve seen in schools, the problems in Catholic schools are far fewer than in public schools. Just know that these problems can and do exist.
You’ll need to find a good Catholic school, too. Make sure you find one that is orthodox and has good parental involvement. There are some bad Catholic schools out there, I’ve heard, about how kids are never really properly formed in their faith, they don’t know who the Pope is, etc…
But most Catholic schools do require uniforms (good for structure and less distractions in the learning environment), have smaller class sizes, and more parental involvement. If your child has special needs (special/gifted education, etc.) a Catholic school may not be able to accommodate him/her. Catholic schools also may lack facilities (cafeteria/hot lunches, gym) and extracurricular activities you may find in public schools (certain sports or band).
Don’t worry about cost. See if you diocese can help you. If you really feel Catholic school is right for your family, the school and/or diocese may be able to help you make it happen. Good luck with your decision!