Help my 19 month old has aggressive behaviors

One of my toddlers in my class has been biting, pulling hair, and pushing since they were 14 months old. I have encouraged using words. They are getting quite a few. They are using no no and mine more and more. The aggressive behavior is often over a toy. I have multiple of toys and J give them others that are just like the one they have. I also use redirection. Time outs are not allowed. I also show soft and gentle touches. I need help. I'm at the end if my wits with them. They aren't doing it with their parents so hey aren't able to help. They are also expecting a baby in 3 weeks. I know that can be part of it the behaviors. I need some advice. Help please.