I thank there are several keys to the done by noon thing. If you read the Hazels how to fit it all in part in the TM. The Hazels train there kids to get up make beds, clean rooms, and make breakfast, clean up breakfast and I believe chores. They have to do this and be ready for school by 8 and they are usually done by noon according to the TM. They are focused on school and try to eliminate most unnecessary distractions.
So you either have to train your kids to get up and be ready by 8 and maybe train yourself to too. This might mean you get up earlier to make breakfast for your kids if they're not just having cereal (I don't let my kid make pancakes for example all by herself so she helps or I make it.)
Another key is being organized. If you are not organized and have everything right there ready to go it adds time. You also have to train your children or teach them how to work diligently. Some children do and some need hand holding to do it. I tell my dd the longer she takes to do whatever school work she is doing (usually spelling) the less time she will have for other things (I don't say for fun stuff because it tells dd school is not fun) like playing with her toys, reading books, time on the computer. So if you can point out to your child hey you spent 10 min moping or not doing your work the consequence (natural one) is less time for other things. If dd is taking way to long she looses play time or computer time.
Another key is the time the Hazels spend on each subject. Most things they spend 15 to 20 min. But it's amazing how much extra time things take when you or your kids dilly dally. The key is focused attention.
I think too that a lot depends on expectations if you expect something to happen it will more likely then when you are wishy washy.
You also have to take your child into consideration if your child is not neurotypical (has some learning disability, add, autism or some other issues) school is going to take longer. Your child may need more breaks or you may need more breaks.
I have a dd on the autism spectrum but even with her I have found when we start school between 8 and 8:30 we almost always get school done before noon. (unless she is having a bad day or I am

)But if we start at 9 we have a few things to do in the afternoon.
Another suggestion that Julie makes is having a set time for school. This means you do school from 8-12 or whenever. You only do school things during this time. That means not answering the phone, not doing laundry, chores, or any other things. And you end school even if a lesson is not finished (some people make it homework especially if child was lazy) You will have distractions but you don't have to answer the phone. And when you do have a distraction like taking care of a baby or preschooler if you teach your kids what to do during those distractions. Like I have my dd do her math drill or if it's not instruction day for math then she does her math or book basket or some other independent activity while I'm busy. But if your distracted and your kid doesn't know what to do the ten minutes you spent on the phone is wasted because your child wasn't focused on school work. If they know what to do you can eliminate 10 min of school time by doing some other school work they can do independently. I think this gets easier as they get older. It has in my case.
I think there are a lot of factors that go into getting done by noon many I haven't mention and each family is different and has different needs.
Try not to get frustrated with not getting done by noon. But if you really want to get done by noon take a look at the factors that are effecting you and see what you need to do. This won't happen overnight but you will make progress!
May God guide you as you decide what you need for your family