really depends on where you are and how clever your ds is and also what he has been doing in school.
I have 2 in grammar schools and now do 11+ tutoring. In our area it isn't massively over pressured wrt no of places v. no of kids sitting, but it is also a super selective system, not a general grammar (so top 5% of kids not top 30%)
In our area it is a CEM test. At the minimum I would say you need to go through the topics in the CPG 11+ prep books. There are some maths topics not covered in school yet. (ratio, percentages, probability) There are also maths terms that they should know, which aren't always drilled in in school, eg factors and primes.
Depending on the school and how well they have been taught they may or may not have covered the rest, and then it is a matter of revision.
I have had students who sail through all the examples in the books, who have already covered all the material at school, and whose natural vocab was really good, so they were fine on verbal reasoning etc.
With those students, they really need exam technique prep. At least one mock test under exam conditions (but could be at your kitchen table) using the correct answer sheets, so they have practice filling them in. Talk to them about timing, if you get stuck on a question, give it a go and then move on, keep going, don't wasted time on questions you can't do, if it is mutiple choice, always put an answer even if it is a guess, and also if it is mutiple choice use the answers that are there to help you work it out (eg, if something is mutiplied by 2, then all the answers which end in an odd number are wrong)
Non verbal reasoning practice is good too as that isn't done at school.
These student could really have got away with just doing a couple of weeks intensive over the summer (that is what I did with dd, as I couldn't get her to do any before the summer holidays!) and a mock test.
But I have had other students who are great in one area eg English and poor in another, and we have spent the whole of year 5 working hard on those areas to try and bring them up to scratch. Those kids need a lot more work over longer time.
If I had a student who was poor across both English and Maths I would recommend to parents that they didn't continue with tutoring for 11+, as it is unlikely they would pass, and even if they did, they would struggle at grammar school.
Without knowing your child it is really hard to say.