Who knows what fronted adverbials are?

A few days ago I looked at my grandson's English home schooling worksheet. It was quite incomprehensible - all about the structure of language, including the above mentioned. He is 7.

I then saw Michael Rosen's piece in the Guardian.  Needless to say, there are letters in "defence" today from a secondary school teacher and a university lecturer, basically saying that technical knowledge enables creativity. I can see there's maybe a case for this for older children - but 7 year olds? Have they ever met one?

Update 28 Jan: I wrote to the Guardian but didn't get my letter published. However they published two expressing the same views as me.