Parents say pupils are being denied basic human rights by a school's decision to restrict access to toilets with lockable gates.
The move at Hundred of Hoo Academy has sparked outrage among parents, who say some pupils are restricting how much they drink in order to avoid draconian rules on using the bathroom.
The academy this week said they had a long standing policy by which students needed a pass to use toilets during lesson times, but admitted new 'shutters' had recently been introduced.
Lauren Jewiss, 32, from Hoo, said the rules were 'ridiculous' and explained pupils have to go to Student Services to request a key for the toilet and then take the key back.
"It's a secondary school and it's big school - sometimes they have to go from one side to the other to get the key.
"If someone's got a bad tummy or something, it's going to be difficult for them - it's not fair. One of the girls was on her time of the month and they wouldn't let her go. Her mum said just get up and walk out - which she did and then she got in trouble.
"It's basic human rights to go to the toilet. Some students aren't going to the toilet in the day and they have half an hour bus journey home before they can go.
"They haven't been able to go at lunch because there are queues at lunch - so they have to split their lunch time between eating and queuing for the toilet."
She said discussion on a parents' Facebook page had led to calls for a petition, with a number of parents slamming the system.
"People are saying it's like prison," she added. "One mum said her daughter almost had an accident."
Commenting on Facebook, one parent added: "My daughter already didn't drink enough at school because of not having enough time to queue for the toilet at break times, so now she drinks even less. Constantly coming home with a headache."
One parent responded: "This is the same as my daughter", while another said "my daughter refuses to drink at all."
Another said their daughter refused to drink in the morning before school for the same reason, while others said girls had not been able to change sanitary protection due to the rules.
A statement from the school said it was "renowned for our safeguarding systems and support", adding: "As part of this safeguarding approach we have always closely monitored pupils attendance and punctuality to lessons.
"Pupils are able to access toilets, student services and our pastoral rooms throughout the day but should follow the school systems that have been in place for a number of years, with pupils reminded of them termly.
"There has been no change to policy and pupils are able to use the Academy facilities. We have multiple bathrooms around the Academy and pupils use these freely during break and lunch, as staff are on duty in these areas.
"During lesson time pupils should register at their lesson and use the teachers ‘out of lesson’ pass to gain access to the bathrooms or attend one of the pastoral rooms. This ensures we know the location of all pupils and can safeguard them effectively.
"Like all schools, we try to encourage students to use the toilets at the most appropriate times to avoid lessons being disruptive, however, if a child needs to use the toilet then they are permitted to do so especially when they have a medical condition that may require it more frequently."
And they added: "Shutters are used on site to prevent unauthorised use of the toilets when they are not supervised which improves both student safety and helps avoid any vandalism. We have specifically opted to use shutters rather than doors as this allows a clear view into the communal area of the toilet for staff when walking the site.
"We take our responsibility to safeguard and educate pupils extremely seriously and will continue to support our pupils to be the best that they can be."Kent MedwayChris Hunter