The C.D. Howe Institute just put out a report on the performance of Alberta schools. It's a very interesting read, and you can access it directly here.

This is a valuable tool for both choosing a school for your children, and for evaluating the success of different educational models. The results are based on performance on standardized tests - and therefore exclude those who do not write standardized tests.
Of those schools that were tested, charter schools seem to significantly outperform other schools, even when you control for socioeconomic status. See the following paragraph from page 9 of the report:

The gap between charter schools and all other schools is large and consistent across all three grades. Students attending these 10 (seven of which offer Grade 9) larger charter schools outperform their counterparts at public, separate and private schools. Why might the gap be so large? First, it is possible that charter schools are able to select the best students out of other schools and reject weaker applicants. Second, charter schools may be able to hire stronger teachers. Third, charter schools with mandates to match the interests of students, teachers and parents may produce better results. The large and persistent gap between the charter school results and the results at other schools, even with controls for observed student background, would seem to merit further investigation.

As noted, the report does not offer conclusive evidence in favour of charter schools, but it certainly should elicit further conversation. As an organization, we support removing the cap on the number of charter schools, eliminating caps on enrollment, and removing the onerous requirement that charter schools regularly re-apply for their charter.