For prospective 11+ parents, I concur that taking the Sutton mock is a good first step, I think the earliest one is in May, and you would know, whether the effort you spent was enough (whether 1 hour a week or 1 hour a day). Over 1000 sat the mock and I think it is quite representative.
If you score within say top 20% in that with minimal effort up to that point (say 1-2 hour a week), then you have good chance for good schools (except the very top ones) even you continue with minimal effort. If you are within top 10% say, then good chance for the very top one (private or grammar) but since everyone will step up a bit after that time, maybe you also spend a few more hours every weekend.
If the results disappoint you, then you still have a few months including the summer holiday to catch up. And there are several mock tests.
Only that the mock tests don't test VR and NVR (but many schools don't test anyway) and creative writing.