A couple of thoughts...
Was this advertised on local radio?
Did they imply that they were somehow really "connected", most probably with the Disney Channel or Teen-Nick?
Do NOT sign anything the day of the 'audition'.
Do NOT pay for classes or the agency's recommended photographer.
If you feel pressured, LEAVE.
If they pressure you to sign a contract, tell them you need to take the contract to your lawyer.
If it sounds too good to be true, it probably is.
I tried to look "Talent Insider" up and found one website that might be them. I've never heard of this (agency? manager?), do they have a website or a phone number to contact for more information? If I had some more infor, i cold do some digging for you.
Sounds like it probably a scam to me, doesn't pass my smell test...
agnes!