6 yeah old and speech

[nis123]

Hi my daughter will be 6 in June. She has had her language level tested and we were told it is at a level of a 3 1/2 year old. My daughter is bilingual. Her father speaks norwegian and i english. I am the only person that speaks english. She was tested on her norwegian. Up to when she was 3 1/2 she only saying words in both languages and had her own language. We were told to send her to kindergarten and being around other kids her language will develop. We did that and in a matter of 4 or 5 months she was acutally making sentences but lost any english she spoke. She understands what i say to her in english. She answers me back in norwegian. I was told by the speech therapist that i should not send her to school in august but keep her back in kindergarten another year. I disagree. I believe if she is with kids her own age 6 and up she would learn from them as proven before and her language will get better. I was told that would not happen and keeping her back with the 3 and 4 year olds would be better. She is a very shy child and does not speak to people she does not know. Can anyone help me with this?what should i do?