Are there early childhood signs of schizophrenia?

YES. A good number of people who are diagnosed with schizophrenia as adults have evidence of information processing irregularity in childhood.
Nothing specific. This has been an area of intense interest for many years. Schizophrenia commonly appears in late teens, and we would love to be able to detect who is at risk earlier to try to prevent the life disruption it can cause. Some studies suggest that those who later develop schizophrenia tend to be loners and more problems with peers--*but* most people like that don't go on to develop schizophrenia.
In retrospect. There are a number of abnormalities commonly seen. But those abnormalities, if recognized in childhood, don't predict that the child will develop schizophrenia. They abnormalities with an unknown future.