Parents: Is this all I need to do?

I just asked about how to un-enroll my stepson from school. I called the school and they said that I would have to come up there today and fill out some papers and that they would consider him un-enrolled come Monday. They said that our state really monitors children in school and if he was not enrolled in a new school on Monday or Tuesday, that it would throw up a red flag.(Texas) I am off work today so I told my husband I would take care of this, but I can not reach his ex on the phone to make sure that she is en-rolling him on Monday and my husband isn't answering his cell either. If I go ahead and un-enroll him and let them know that his mother is getting him back this weekend, will it now be her responsibility to take care of the new enrollment?