"Personally, when I am on my period, I experience really painful cramps, meaning I cannot walk without having to be bent double.
"Sometimes, I get so dizzy I pass out or vomit – obviously on these days, I would not consider myself fit to go into school.
"The fact Dr Watson sent the email out to the whole of sixth form as well, including the boys, is just making boys think it isn't bad and that they shouldn't be sympathetic.
"I am now quite uncomfortable to think of my next periods and how I will manage them at school, as I'm sure the majority of girls are."
Watson said there would always be exceptions, but that most students on their period should be able to make it to class.
"Anywhere where you work you can't take two days off for being on your period," she said.
"If it's just an ordinary period, you should come into school – unfortunately taking that time off is not how society works.
"The email is about attendance, that was simply the point – my slightly tongue-in-cheek way of saying it maybe got to some of the girls, but the email was to get across the message to be in school."
But the teacher admitted that sending the email to the entire school was probably a mistake.
"I probably shouldn't have done that and perhaps it was a bit foolish of me," she said.
Watson said there was plenty of support for students suffering period symptoms and that there was a "huge amount of time supporting students with issues and health-related matters".