can anyone tell me what the raw mark needed to pass will be for a child born in December?

Is the percentage on each area as follows?:
30% maths
20% NVR
50% english (so 25% VR, 25% comprehension/SPAG)

Because my sons biggest weakness is comprehension, i'm wondering if he still has a chance......(I know no one can answer that, but I'm just putting down my thoughts)

The raw score needed will vary with the cohort each year.
As far as the papers go, the following is from the TBGS website:

https://www.thebucksgrammarschools.org/news

Thank you Scary mum, thank God I asked! no idea where I got my percentages from!

On the raw scores, I guess I was hoping to get some idea maybe from previous years scores.

it doesn’t work like that, OP.

Each year, the children are marked in twelve groups, accordong to their birth month.
say 2,400 kids took the test? there would be 200 in
each monthly age group.

So then they look at the raw scores for those 200 kids (which will
be different every year as the exam questions are different and the abilities of those Dec-born children may be a little different too). They set a “pass point” where 33% of the kids will pass and 67% will not : this is called “cohort marking”.
They then use a normal distribution curve thingy to mathematically translate the raw scores from the paper into an end “mark”.
As Scarymum says, the paper sections are not equally weighted, there’s a proportion for maths, English VR and NVR, and those combine to give an eventual “mark”.
If it’s 121 or above, ie in the top 33% the child “qualifies”.

so knowing last years raw marks honestly tells you nothing.
To pass this year your child must outperform 2/3 of their cohort who take the test.
that’s all. it’s a bit brutal (and flawed) but that’s the system we have.