I'm still a SP, well past your benchmark, and my accountant sees no reason to change it. I'm well protected with insurance, which is far better than relying on a corporate veil or organizational protection. That may have some bearing on her decision for me to remain a SP.
However, one line in your post caught my eye,
everything is away from kids so there is zero chance of them tripping over my stuff.
There is never a zero chance. If you keep working for any length of time, I can almost guarantee something will happen in the future no matter how careful you are. Things just happen, and in strange ways sometimes. Maybe its minor, maybe not. But if you are shooting at schools without insurance, and assuming there is a 'zero chance', you are taking a risk that could put your livelyhood and life savings in jeopardy. I'm even surprised they haven't asked for a guarantee of insurance, which seems mandatory whenever I step on a business property.
Even if something minor happens and a parent has the funds to make it a legal issue, you could still be left in serious debt just from protecting yourself. At least if you had insurance, even a minimal amount, the insurance company will be fighting the issue right beside you, and not landing it all on your shoulders. Heck, even if you just added $.50 to each portrait, with average volume you could have enough to cover a basic policy.