1. You don't have too many choices, most likely go to public school, you have to look at the admission conditions of each private school even you have enough money for it.
2. English is the most difficult obstacle for a 16-year old. suggest starting from Grade 8, the teenage can have one year to learn English before high school. everything else is not an issue. ESL can help, but don't count on it.
3. Admission procedure is the same for all public schools.