As I was saying — you have been introduced to spells that have been complex, inappropriate to your age group and potentially lethal.
The purpose of Potter’s meeting with these students,’ continued Professor Umbridge, ’was to persuade them to join an illegal society, whose aim was to learn spells and curses the Ministry has decided are inappropriate for school-age -’
There are no more uses of "appropriate" identified with this meaning, but check unspecified meaning below.
’Before we begin today’s lesson,’ said Snape, sweeping over to his desk and staring around at them all, ’I think it appropriate to remind you that next June you will be sitting an important examination, during which you will prove how much you have learned about the composition and use of magical potions.
As recently as 30ih August, Educational Decree Number Twenty-two was passed, to ensure that, in the event of the current Headmaster being unable to provide a candidate for a teaching post, the Ministry should select an appropriate person.
Your previous teachers in this subject may have allowed you more licence, but as none of them — with the possible exception of Professor Quirrell, who did at least appear to have restricted himself to age-appropriate subjects — would have passed a Ministry inspection —’
There are no more uses of "appropriate" in the book.