Well, my personal reference is as follows:
1. Lisgar: Located in downtown. Best academic high school in Ottawa with the long history
2. Colonel By: Located in Orleans. Well known for its IB program, which is recognized by many universities in United States. But your kid(s) has to finish four years courses(OCDSB) in three years; at the last year, the students will take pre-University courses
3. Canterbury: Best arts high school in Canada, not really good in acadamic program.
4. Earl of March: Located in Kanata. Fast-growing high school last few years. Students are from middle class families in Kanata. Like Lisgar, it is well known on the accomplishment of Acadamics.
5. Ashbury: Beautiful campus located in Rockliffe, which used to be richest city in Great Ottawa area. The school runs IB program, and it has very good relationship with US universities. If you think your kid(s) is a material for Harvard University, it worth you to give a try.