M.J.
There are lots of things to think about when making this decision. I have 2 kids in Catholic school (not St. Walter's) and 1 in public (we just switched this year).
Advantages of the Catholic school are there is a smaller community, they can kick out problem kids (it takes awhile, but it does happen), the teacher are there because they want to be and they can teach religion. Oh and the uniform is a real plus. Academically they do push the children harder and make them do more projects like a science project.
Disadvantages are bigger class sizes (the younger grades at our school have a full time aid), constantly being asked for money, LOTS OF COMPETITION in academics and athletics (and it's not always the kids) and dealing with people who think money allows them not to follow the rules. You also might have to drive your child to school every day.
Advantages of public school are that there are gifted programs if your child falls into that category, you get to know people in the neighborhood, maybe you can walk to school, they don't expect everyone to have a computer or a mom on call to take the to the library at the drop of a hat.
Disadvantages of the public school are that they don't seem to push as hard as the private (science fair project is not required), they have to take any child, you have to worry about clothes and here it starts so late (9:15 for elementary).
Each child is different and only you can figure out what works best for your boys. I would talk to your neighbors and visit the schools.
At the private school ask about extracurricular activities BESIDES SPORTS. One of my kids is not a sports kid and there wasn't much else for him to do with his school friends. Ask about tuition and what is the standard increase because it does go up every year. Ask how much they expect you to volunteer.
I'm sure I could come up with more if I thought about it, but some kids are waking up. Good luck!
M.