Concerned about 6 year old

My six year old stepdaughter is in kinder. She has some behavioural issues and it’s possible she may have adhd/odd.My husband and I have a 2 year old daughter. My daughter is very bright. She can identify and name every letter in the alphabet, count to 20 on her own, speaks very clearly, etc. You can have a really decent conversation with her and I’m so happy with her development. I’ve worked hard to teach her.We are really concerned because our 6 yo, who is supposed to be learning her letters all day at school, still can’t identify and name them. I’ve tried so hard to practice spelling her name with her but no dice. I bought a book that came with a pen that you can wipe off to practice writing all the letters. They’ve put her in a special “reading program” at school. She still speaks similarly to a toddler in terms of pronunciation. She still struggles with her ‘r’ sound. For example, she still says “buhguh” instead of burger. I’ve paid attention to all her cousins and all the other kids in the community we know, and none of the other kids are still struggling with pronunciation the way she seems to be. Most kids her age seem to be speaking really clearly by now. It’s really worrying because the two year old is learning a lot quicker than her. I’m not sure if this is related to the learning issues but her teacher is coming to us at least twice a week saying it was a hard day and she got in trouble, usually for throwing a tantrum in class and not listening.Does anyone have any insight as to what could be going on here? via /r/Parenting https://ift.tt/38l4CYV