If a child sometimes asks to go, let them, of it is constant one random day then have them check in with the school nurse, it could be the squirts, so contagious, or it could be a UTI, so may need a doctors visit.(either way they may need to get sent home)
But if it is the same kid day after day hour by hour? Make them hold it. (Medical conditions notwithstanding)
The thing is, unless youre at the bathroom door you dont really know if they are actually taking a wee, though pretty sure you’d hear the squirts from the doorway.
Always take young chldren at their word about needing to go (aforementioned reasons of previous posters)unless they have been shown to be liars.