No, they don't necessarily contradict each.
possession of proof of purchase does not mean ownership, at least not in my country. Alternatively you can own something without possessing proof of purchase.
They contradict what evidence he has of the transactions necessary. Given his sequence of events and statements, neither I nor you can say who owns the devices, when asked he hasn't clarified the position much, no reference to what his parents or he signed up to, no reference to how the fees were described, basically no "working" for the "solution". Being at school he should understand that gets you minimum marks.
If the school has proof of purchase then the school owned it. Unless he can show proof of purchase, even by school statement, then the school <still> owns it.
Must say for someone who completely misunderstood a poster's reference to the OP's other posts, and started to make off the cuff accusations on the basis of that misunderstanding, you really are starting to chuck rocks in a glass house...
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What we're witnessing here is the creep of totalitarianism from the mainland into the schools of Hong Kong...
LOL - no I think we are witnessing a school trying to control their network to prevent rife copyright theft and network security issues - a complaint that has been levelled at China for years, the irony is that now we see that starting to be reversed, it is the Westerners criticising the school...just too funny.
At the end of the day the school doesn't have to teach him, and if he can't use the MBP in class his education may suffer (lets assume for a minute there actually IS a sensible reason why the school encourages/provides these machines at all, perhaps they are quite vital for in-class work? Perhaps the school doesn't provide computer lab for exactly the copyright/scam hosting/hacking reasons??)...but that seems unimportant to you?
If he wants educating at that school he should comply with their policies whether the machine is his or not, otherwise he should go elsewhere.