Caring Start Act of 2017 This bill amends the Head Start Act to require that, in providing and allocating resources for training and technical assistance, the Department of Health and Human Services (HHS) give priority consideration to activities that: support the implementation of evidence-based trauma-informed practices, age-appropriate positive behavioral interventions and supports, early childhood mental health consultation, and prevention of suspension and expulsion; and increase coordination between Head Start agencies and other programs that serve very young children. Such assistance must also, to the maximum extent practicable, assist Head Start agencies in adopting evidence-based approaches to best identify and serve children whose experiences have elicited a toxic stress response. (Toxic stress response can result from strong or prolonged adversity without adequate adult support.) HHS shall fund personnel training in: evidence-based trauma-informed practices, as well as early childhood mental health consultation and age-appropriate positive behavioral interventions and supports; and helping children who are victims of trauma or toxic stress.