for sure toronto has options for students to attend other schools that aren't in their catchment area. i went to one myself, as did my sister (and our neighbourhood highschool was fine, we were both just talented and interested in areas that the school didn't cater to). for myself, i had to apply and put together a portfolio, but it was dependent on the demand each year. some years all you needed was a recommendation from the art teacher or department at your junior high. my sister only had to apply i think, and have certain grades in math and computers. several of my friends left our arts school to attend alternative schools that had a more self-directed approach, and they only needed a guidance counselor to tell them about the options and send a recommendation.
toronto is very special in that many of their highschools and a fair number of junior highs have specialized programs, and as long as your kid shows some kind of interest and ability in a certain area, it's a pretty good chance that he can find the right place to go. they don't just move people to other schools because "the neighbourhood is crappy" or "the school has a drug problem" but there are options. the guidance counselor in his junior high or elementary school can help with that.
there are certainly private school options in toronto as well.