We have different levels of detention (using the detention type field), most staff will only want to put a student into the lower levels so allowing them to pick from an open list of upcoming detentions of every level makes it harder than it need be for them to select a suitable one.
While I think it correct that teachers should be able to see if their pupil is already in any upcoming detentions, if there were access rights applicable to different detention types then higher levels could automatically be displayed in the pick list as read-only (so that they could not select them), in a similar way to sessions that have passed the cutoff time.
And in a similar vein, it would be useful for a teacher to specify the level(type) of detention they want (from among those they would have access to), and then only be able to pick from the slots of that type, e.g. with a drop-down filter at the top (similar to the Term one), that greys out detention sessions of the wrong type.
