I don't think any reasonable person would deny any of the kids a day off today - especially not one who was shattered enough to break down into tears due to the tiredness.
Stavros also semi-ed on the Tuesday which gave them 3 more days rest/recuperation, I guess though they aren't as fit as Aidan is it still shows how draining it is - even for something less physically tiring like a singer.
And of course, it's better to take one day off to get right than to struggle into school and then make it worse, or spend more time getting over it. (I've done the latter a few times before) Provided they make up the time and don't get behind it shouldn't matter - though we're talking year 7/8 kids here rather than further up the school where they could miss something important.
Perhaps a case for a clear day between the finals and the semis, at least. That would give them a day or so clear to have a lie-in, get more rehearsal time, and another night's sleep without having to be on BGT before having the final day. I guess them having Wednesday clear for the football didn't help (though I bet titch would have moaned about being on then, as well as the result) because then they could have saved Friday as a clear day.
Regarding the travelling, I think they have pre-decided the semi finalists before they screen the auditions (though obviously they are told to keep quiet about it), they audition in Jan/Feb and we don't see the acts until April so that's plenty of time for them to prepare and decide, so it's just a case of a day to find out when they decide unless they write or something. Otherwise, I think they put the semi finalists up in a hotel - from the reports about Susan this is near Wembley this year - so they only have to travel from there to the studio and they would probably bus the kids back earlier. Slightly less than titch having to go back to Birmingham on Friday which would have been pretty awful. I'd presume they'd kick them out the day after they finished so they would have had to go back yesterday - checkout time is normally 10/11 so he's had no lie-in... No wonder they're tired.