I worked for them, since I was nine. So, yes, I learned from them; we taught each other, any apostates we helped would share a bit of knowledge to be passed along. We had a few successfully escaped Circle mages here and there (though very few), and even one or two actual Circle mages working for us.
Oh phew, it's a relief you're taking this well. I wasn't entirely sure if you were pro-Circle or not. And it's strange to be able to bring this up, after years of working so hard to keep it secret. This was my biggest secret, more so than being a mage myself. That would just put me in danger, whereas knowledge of the Collective could've endangered everyone in it.