From what I understand, the other two teens that were arrested were not accomplices but rather people who hired Curtis to do the swatting for them-- one of them ordered the same school to be swatted twice, even.
Here is the blurb on one teen (the other one seems unrelated to Curtis, just caught in the same sweeping investigation on swatting):
Officers investigating the Milton incident said they learned the accused had planned for the threat — which said explosives placed in the area of the school were going to detonate — to be delivered by an "online" acquaintance.
Investigators said they identified the acquaintance as a 16-year-old from Ottawa believed to be responsible for dozens of incidents across North America.