In California, is it necessary to have insurance when a minor is training with their instruction permit?

I am a minor (17-1/2). My classmates say I do not need insurance to drive with an adult 25+ with my permit. I am reading the instructions and the only thing I see is that you need insurance when you take your driving test. I am in no rush; the only problem is that they are driving without insurance. Does anyone have a source stating what is true; I cannot seem to find the answer online.