They are 10 and 11 and capable of waiting for at most a couple of hours. Use the toilet at break and lunch is surely the standard rule?
You're probably going to get some conflicting opinions on here. This is my personal view though.
As with any job you should use your discretion. While it's certainly reasonable to expect children to use the toilet during break, there may be times when them needing the toilet during class is unavoidable. To deny someone in clear need is inexcusable and should they soil themselves as a result, you're going to end up with a distressed child and very angry parents.
There are I'm sure ways you can come up with to sort the slackers from those in genuine need. But a blanket ban is IMHO unreasonable.
Only use Helpful answer if your problems been solved.
I teach year 6. I don't let children go to the toilet during lessons. One of the mums complained because I didn't let her daughter go to the loo during the afternoon yesterday.
There are plenty of children (and adults) whose bodily functions don't conform to your idea of planning when to go.
Added to that, "holding it in" can actually cause damage internally as we are not really designed to stop ourselves and as girls especially get older, there have been multiple cases of them being prevented from going to toilet on their periods, causing pretty serious mental harm.
At work, if I need to go to the toilet, I go, and only the most oppressive of employers prevent this, and they usually get rightly slammed for it.
If you need to go, you need to go. It is completely unreasonable to prevent this. If children are using it as a reason to avoid classwork, you need to find ways to prevent that, not withhold what should be a right, not a privilege.