It can be hard to imagine teaching all of your children at one time if there is a spread in their ages, but it can be done. If your students are all within a couple of years of each other, it's likely you can pretty much lump everyone into the same grade level, perhaps having everyone on different math or reading levels. There are many subjects, such as history and science, that can be done together to save time and materials.
At one point in our homeschooling journey, I had a spread of students that went from Pre-K all the way to 12th grade. And believe it or not, we STILL found a way to do a subject somewhat together! This is part of the beauty of homeschooling--you aren't running a one-room schoolhouse, you are teaching your family; and families should be together when possible.
Here is the thing you must know: It will likely not be possible to do everything together all day. It's probably not even a good idea. There should be different types of learning throughout the day; independent, small group, and whole family. All have merit. Many homeschooling families like to begin the day together and then split up, with Mom (or whoever is teaching) taking a student or two aside and working with them, while others do independent work. Later, Mom can switch to working with other students while a different group gets independent time. Morning time together can consist of a history lesson (aim for the older students and let the younger ones simply listen in and absorb what they can), Bible time, poetry reading, vocabulary lessons (my 3rd grader is currently learning SAT prep words and is unaware they aren't for her), reading a book out loud together, etc. A great place to get ideas for this morning time is to search "Morning Baskets" online. There are whole Facebook groups devoted to the concept of morning baskets and you can truly make it what you want and need. A homeschool mom with a 1st grader, Pre-K student, and tagalong 2 year old will have a very different morning time than a mom with a 10th grader, 8th grader, and 5th grader sitting beside her. Don't compare your homeschool to others, but get ideas from them!
One of the benefits of working together when possible is that the younger students learn from the older ones. Also, they are exposed to materials much past their grade level early on. So, when those things are on their lesson plans, it won't be new to them. Also, teaching things to a variety of ages forces the teacher to break down her explanations for the younger set, which can benefit the older students by helping them understand and not being embarrassed at needing to hear it in a more elementary way. Mom might be talking to little brother, but big brother might also benefit from the extra explanation. Also, in a group, some children ask questions that other children would not think of. There is discussion of ideas and materials. There are many benefits of working together!
As I mentioned earlier, math and reading independently are two things that might need to be individualized. Everyone will need to go at their own pace, however fast or slow, in those subjects. History, Science, Bible, grammar....these tend to be easier to do in a group. The year I had everything from Pre-K through 12th grade, we studied Anatomy. Guesthollow.com has Anatomy curricula for all levels. We were able to do individual assignments and projects, while sharing some projects, watching videos together, and even overlapping books. It was a benefit to all from the oldest to the youngest to learn this way. Some curriculum companies really cater to families working together.
Now what if you have an only child, or just a couple of children who don't work well together? Well, first of all I think learning in a community (especially with one's siblings!) takes practice. Especially if your children have been in public school they may not be used to working with a group of others of a younger age. In public school, kids rarely interact with those who are more than 10 months older or younger than themselves, after all. So some teaching, modeling, and patience are needed here. Don't give up on the idea after a brief time. They'll get used to it. But it might also be a good idea to work with another or a few other homeschooling families to build that learning community. One day, I will have only our youngest daughter at home and I will need to reach out more to find a group of kids she can do school with sometimes when her siblings have all graduated. Learning cooperation, patience, and working with others is important and really can encourage hesitant students along.
I think if you find a homeschool in which the mother is teaching each child 5 or 6 individual subjects, you will find a very frazzled mother and a very long school day. Overlap what you can and lump those kids together whenever possible to save yourself some time, effort, and to reap the benefits of learning together!