Personally, I am - horrified is probably too strong a word, but certainly disquieted - that the letter is so poorly worded in itself.
One of the roles of a school is to effectively communicate with people in the community. How many threads have there been here over the years with 'the teacher said this to my child' and nine times out of ten the response is no, calm down dear, the teacher would not / could not / did not and your child obviously misunderstood.
And this isn't the spoken word where occasionally something slips out as it were and you think 'oops' - I am not infallible and once or twice have accidentally upset a child by saying something with something of an ambiguous meaning but this is a bit different. It's written down, it's been thought about, considered. If she'd been trying to persuade a reluctant child and parent to join something and blurted this out I'd be very sympathetic.
So as to the letter - well firstly, it really isn't clear at all what the meaning is. I understood it to be a nod to extremism but even so, you would have to be exceptionally obtuse to somehow think that a gardening club aged nine will help steer someone away from terrorism in a decade. I understand the point they were making but it's so badly worded as to be completely lost.
Also, I hate the line about sexual exploitation. There is an inference there that if you don't join a club and are sexually exploited, well, silly you. Should have been an eco warrior
then perhaps it wouldn't have happened. We know that the line between keeping yourself safe and victim blaming can be difficult but I think that letter majorly crosses it.
Very foolish.