I think early teenagehood, and maybe late teenagehood could be preferable to childhood... but that might be because I'm a teenager at the moment. So I'm loving it more than childhood.
Everyone in my GCSE Maths set could do something like that - our teacher wasn't bad, but she was dopey. We were all working out the maths she gave us before she'd finished it... she was even asking some of us how to do things if she couldn't understand it.
Teachers... deary me.
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That's another thing... you'd be an absolute devil at cards.