I started having auditory and visual hallucinations at the age of 13. I did act manic at times but that didn't get out of hand until later. But I have schizoaffective which is a bit more complex although I have made a full recovery from that (you can read through my posts for more information). It was a terrifying experience at first and I had delusions that aliens were coming into the house overnight and would abduct me and that is only one of the mentionable ones. No one else knew what it was either and thought I was purposely avoiding people. Education is essential for people. I started medication on my own at age 18 and without the support of others at first.
I think the reason I never received treatment for it until later in life was because everyone though I was just being imaginative and I was too young to express myself to convey that I wasn't imagining things and then I just grew up a thought for years it was normal.
I remember having hallucinations at age 6. I watched Outer Limits and at school I saw the alien bug from the show come out of a crack in the ground. I have never forgot it. When I was in my teens I often saw a hand put a coffee can down in my car or on my bed and a tarantula come crawling out of it, and I am terrified of them! Depending on your age, there might not have been any treatment protocol for kids your age. I don't even think they thought kids my age back then (late 50's and 60's) HAD mental illnesses.