Almost 7 yr old not potty trained

How abnormal is this?

My stepson will be 7 in April. He’s still not potty trained. My husband and I have been pushing his mother to have him medically checked out for issues and to see a therapist in case in something more. She refuses and says it’s “normal”. She puts him in pull-ups every night, and he has to take a change of clothes to school for accidents. His teacher is in the habit of frequently reminding him to use the bathroom at school. He can only go 1-2 nights in a row without accidents. He has absolutely zero motivation to work on this and his excuse is “my mom says I’m still learning”.

We’ve been actively fighting with his mother for over a year now to find out what’s going on, but she’s still refusing.

Help!