I imagine that you can call them directly to upgrade to VIP. My family and I were allowed to sit anywhere with just the general admission tickets. There was no VIP area at the School of Rock event that we attended.
You can purchase the tickets to the show, then purchase the VIP, or the other way around, but you have to have at least a concert ticket in order to get in.
The VIP area is the upper stair case seating by the front door. When purchasing tickets online you can choose VIP if it's available. To switch tickets, I'm not sure. But Simon is the manager if you need to talk to someone.
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