Teachers refusing bathroom to kids. Fair or not?

I currently live in Australia and go to an Australian High School. There's a rule where you have to get a bathroom pass to use an office toilet during class time to prevent jigging or meeting up with friends/v4p1ng and all that sorta stuff.

Sometimes teachers refuse to let you go to the bathroom. Do we seriously think this is fair? I understand that we can go at break but I cant go to the toilet in the span of 20 minutes especially when the bathrooms close 5 minutes before the bell rings.

And its not like as soon as the bell goes off for break I automatically need the toilet and have time. 

When teachers say, "You should've gone to the bathroom during Recess." Its just pmo. Does anyone else think that during class when yous suddenly just realised you need the bathroom, you go "oh should've gone at recess when I didnt need to"? 

Honestly I just want opinions. Do we think Teachers refusing bathroom during class to Kids is fair? Is it illegal where you are/should be illegal? And in your school do you only have the singlular office toilet to wait for when you get a pass?

(Kind of a rant/Js wanting opinions)