Actually, by law they HAVE to allow it to stay with the child at ALL times. They can not just cut off the child's communication ability when they leave the school environment.
Sue, I know your daughter is older so this law may not have been in effect yet. I know that my professor was instrumental in helping implement it.
Ohyea if anyone wants to know more about AAC go to the website
www.AAC-RERC.org. There are webcasts and information put out there by the leading researchers in the field to inform parents and professionals (SLPs, OTs, PTs, Teachers...) about AAC for both kids and adults. There is one on AAC and litteracy and on on AAC and young kids (birth to three or four) as well as many more. Check it out!