Daughter lives with the other parent. We were never married or lived together

Ok my daughter just turned 5. She started school and is living with her dad. She is having a lot of problems. She's having fits, crying, running from authority. Her teacher said she is youngest in class and that she may not ready tell next year. He "her dad" cares more about the cost, not what's best for her. He said he cant afford to put her any where else. What do I do? Help me, talk to me.