If my dd doesn't pass the Kent test, are we able to send her to a comp but apply for a place in year 8 and see if she can pass their entrance test instead?

Which grammar schools have their own test at Y8? I know of one or two eg Cranbrook School who have an additional Y9 entry point via Common Entrance, but that’s it?

Ah, I think I get what you mean now. There is really very little likelihood of getting a Y8 place as most grammar schools, certainly in West Kent, are hugely oversubscribed and applications made after Y7 are normally rejected on the grounds the year group is full and over PAN, even if a child meets the selective standard for the school. I think it depends on the individual school as to the assessment method used eg CAT testing etc. It's probably best you contact the school(s) you're interested in directly to see what they say. But in the meantime, good luck to your DD - she may have done better than you think and will get in at Y7!

At DD's grammar (not Kent, but Kent border) one place came up at end of Y8 and as a result they have a new Y9 person but not in DD's class. I gather all those on the expression of interest list had the option to sit an age appropriate test and competition is fierce for that single place. They are not just competing with those who didn't get through at Y7 but also with those who have children at private schools who find they struggle to afford fees, from those who have moved into the area etc, so whilst I can't say for certain I would surmise that competition is fiercer at these later stages than Y7.

I know a boy who moved to Skinners in year 8. A child moved abroad hence a spare space at Skinners. Skinners contacted everyone on the waiting list and about 30 boys sat a test in maths, English and science and whoever got the top marks got the space. So it is possible to get in that way but hugely difficult and certainly no guarantee.