This is the question I'm asked more than any other, and the honest answer is: it depends on your child, but later than the most anxious corners of the internet suggest, and earlier than a last-minute scramble.
The typical timeline
Most families I work with start structured preparation at the beginning of Year 5, giving a full academic year before exams in the autumn of Year 6. For most children, that's about right. It allows time to build skills steadily, cover the reasoning question types without cramming, and leave the final months for timed practice rather than first meetings with new material.
Starting earlier than Year 5 is rarely about exam content. What genuinely helps in Year 3 and 4 is much simpler: reading widely and often, knowing times tables cold, and being comfortable with core arithmetic. A child who arrives at Year 5 with those foundations is in a far stronger position than one who has been doing practice papers since Year 3 but reads reluctantly.
Signs your child is ready to start
Rather than a date on the calendar, look for readiness: secure times tables, reading age at or above their actual age, and the ability to focus on a task for twenty to thirty minutes. If those aren't in place, the first stage of preparation is building them, not buying reasoning workbooks.
What if we're starting late?
If you're reading this in the spring or summer of Year 5, don't panic. A focused six months can achieve a great deal, particularly for a child with strong fundamentals. The priorities shift: identify the target schools and their exam format first, concentrate on the highest-weight skills (usually comprehension and core maths), and introduce timed conditions earlier. What a shorter runway mostly costs you is slack, so a clear plan matters more.
The risk of starting too early
There's a real cost to overlong preparation: children burn out, and the exam grows in their minds into something enormous. I've taken on pupils who had been prepping for two years and were thoroughly sick of it by the time the exam mattered. Eighteen months of steady, low-pressure work beats three years of drilling every time. The exam should feel like a challenge they're ready for, not a cloud that has followed them through junior school.
What preparation should actually look like
In Year 5, an hour of tutoring a week plus twenty to thirty minutes of practice most days is plenty for the majority of children. Little and often beats marathon weekend sessions. And through all of it, keep reading fiction together or alongside them; a rich vocabulary is the single most valuable asset in every version of the 11+, and it can't be crammed.
Every child is different
Some children need longer to build confidence; others get bored if the runway is too long. A sensible starting point is an honest assessment of where your child is now against where their target schools need them to be. That gap, not a rule of thumb, should set your timeline.
If you'd like help working out that gap, the easiest first step is a free 15-minute phone chat.