mrz - unfortunately some schools do - at end of KS1 DS couldn't do number bonds to ten, even on fingers, couldn't count in two's, five's, or ten's. He couldn't use a ruler, knew 2D shapes but not all 3D, + and x were the same as were - /. Didn't understand the concept of 'more than', 'less than', didn't recognise coins, yet he obtained a Level 2 for Maths.
English - DS only learnt to read in the December prior to KS1 tests, but his comprehension lagged way behind, he couldn't write independently. He obtained a Level 2.
This was back when tests were externally marked.
His experience of KS2 tests was similar to that of MK1993.
Start of KS3 DS was put into a class of 10 children that the school had to put in place quickly at start of term for children who had arrived unable to meet their NC levels - apparently 1 or 2 had L4's in English, but couldn't read!
How far below their levels they were, as parent's we weren't told.