Hi, I am a concerned gran

I have full time care of my gran daughter age 18 and has cognitive disabilities, global delay, autism, epilepsy etc.  She attends an sen school in post 16.  I have concerns for my granddaughters right to be treated the same respect as any other mainstream 18 year old as far as it is possible.  Just this week her communication book came home from school stating that she had a full shower in school and soiled cloths in bag.                                                        
"Granddaughter started her day with a shower and very happy about this ! "    by female assistant, unfamiliar to us both.
                                       
I immediately asked my gran daughter if she had had an accident which she said she had not. As there were no soiled clothing I took her word for this.
As I enquired what had happened, her male teacher replied that it was part of the students personal care routine.  I am concerned as I was not informed also that she had her period.  
I felt this was totally unacceptable and a violation of her right to keep her body private.

I do support the fact that our children may need this from time to time or after swimming but not at random to be pulled out of class to do this.  

The response I have had from her teacher is only to send the same email which is a repeat and does not answer my questions and suggests a phone call only.  

Has anyone on this site had any similar problems with school procedures and who implements them.  I am always aware of my gran daughter vulnerabilities and only wish to keep her safe in the future.  I am opposed to her being taught to be comfortable stripping off for a shower at random in front of strangers.  Am I being over protective ?