WTF is going on with British primary school assessment?

I feel for my UK teacher friends... WTF is going on with British primary school assessment?
I always hated teaching English because languages, by their very nature, simply defy clear-cut, 'logical' rules and yet everywhere we're expected to teach rules. Teaching resources online always make bold, absolute statements about grammar points and I often had a niggling sense of doubt about them.
It turns out that linguists actually dispute the entire category of subordinating conjunction! I always found that hard to explain (or understand), apart from that it seems you can move subordinate clauses to the front of a sentence. But the oft-used definition of 'a subordinate clause is less important than the main clause' doesn't, to me, make sense, for example, of the coordinating conjunction 'so', which is basically the inverse of 'because'. As in, "I ate quickly because I was hungry." versus "I was hungry so I ate quickly." In either case, the reason for mentioning my hunger is in giving an explanation for the statement "I ate quickly".
Also 'but' - "I like comic book movies but I still haven't seen Batman v Superman." In that sentence, isn't the first clause subordinate to the second? Because you could replace 'but' in the middle with 'although' at the start, which is a subordinating conjunction?
I thought my own understanding of grammar, from my education and training leading up to me having to teach it, was just insufficient, but it seems like people who ought to know this stuff are equally disgruntled.
Example question from Y6 grammar test, taken from Michael Rosen's recent blog post:
Tick the sentence where the highlighted word is used as a subordinating conjunction.
Tick one.
He was at school BEFORE you.
She did her homework UNTIL dinnertime.
Do not undo your seatbelt, UNTIL the car has stopped.
WHEN the sun is out, we will go outside.
Just what in the hell? Can anyone answer this? It seems from Michael Rosen's update post that a lot of people who you'd think ought to be able to answer a Year 6 grammar question cannot.

My new favourite Japanese word

I love the Japanese word komorebi. It has no English equivalent; try typing it into Google Translate.

I was looking for an image to represent komorebi when I remembered this video I recorded at a folk music festival in Sheffield a couple of years ago. I was lying on my back listening to the music in the shade on a hot Summer's day, enjoying the komorebi so much I had to record it.

Komorebi means 'sunlight filtered through foliage'. What an absolutely glorious thing to have a word for. The Japanese, as if I didn't already know it, obviously have a keen sense of beauty.

What's even better about the word is how it's written. There are 3 kanji in it (the れ is just the hiragana for 're'): 木漏れ日. I tried to figure out what those kanji meant to see how such a cool concept was translated into a word.

Kanji are the complicated symbols that come from Chinese and have meanings but their pronunciation varies from word to word. There are thousands of them and, like English spellings, some people know more than others.

Firstly, I immediately recognised the final kanji, 日; it represents the sun and is often pronounced 'bi'. So this word probably has something to do with the sun.

The first two kanji are 木, tree, and 漏, leakage, which I had to look up. Weirdly, put together (木漏) Google Translate gives the result 'kimo', or 'liver'! I guess the liver filters things, like the leaves filter sunlight?? Why the kanji for tree/wood appears in the word for liver I have no idea.

Add the れ to 木漏, however, and the translation switches to 'komore', or simply 'tree leakage'. I assume that's either Google failing to think of anything more appropriate than slapping the two meanings together, or the Japanese genuinely have a general word for stuff leaking from trees. Which is kinda weird.

Komorebi in New Zealand (photo by me, from April 2014)

An honorable mention goes to 森林浴 ('shinrinyoku'), which translates directly to 'forest bathing', and according to the page which inspired this post means "to go deep into the woods where everything is silent and peaceful for a relaxation". I love me some shinrinyoku.