Making maths fun when our children are younger doesn't seem too difficult. Plenty of great living books, manipulatives, games and hands on activities. But as they get older it is easy to resort to a textbook. We did. And some of my kids were fine with that, in fact some even liked it. Of the others though some loved maths and wanted more, others just needed something different - at least some of the time.
Once our child can read and follow instructions it is easy to expect them to work through a maths textbook by themselves while we get on with other things. For social learners this can be especially disconcerting. One solution is to play maths games together. It's still possible to find them for more advanced concepts. Here is Order of Operations Bingo for grades 6-8. And one for Polygon Capture . Or consider getting them together to do maths with friends. Even if they aren't using the same book they could still work side by side and perhaps help each other out. Sometimes I've even done the maths lesson with a child. I'd work one problem and she'd work the next. Consider a Party School for maths. Pi Day provides a great excuse. And there are plenty of ideas on line. Here is just one site.
One of the problems with maths, especially in the upper levels is that it can seem abstract and irrelevant. Cue the cries of "When will I ever use this stuff anyway?". It's great if you can find a maths connection to something your kids are really interested in.Google quickly turns up promising sites if your child is an art lover or a musician. I've got a trampolinist so the score sheets from competitions provide interesting data for statistical investigations. She's also a keen birder so problems like this appeal to her. If you are looking for ideas Yummy Math is a great site that provides topical problems, activities and explorations tied to the real world. Recent lessons have looked at the Oscars, Leap Year, and a giant Snickers bar among other topics. Illuminations also has some good real world problems.
Another problem with math is that it can get monotonous. It, more than any other subject, is where we are likely to pick one textbook and stick with it, using the same series for the bulk if not the entirety of our child's homeschooling life. Even if we follow that route (and I mostly did) there is no reason why you can't add in some alternative activities, or replace a lesson in the textbook with the same material taught in a different way from somewhere else. How about AlgeCaching, like geocaching but online and for Algebra 1, or a webquest for symmetry? The Actuarial Foundation has a series of free workbooks and other materials on topics including geometry, algebra and statistics. The Mathematical Enhancement Programme provides an entire set of maths resources for children aged from 6 through to high school aged. And all for free. Teachers Pay Teachers also has plenty of individual lessons available for free or at low cost - like this one on multiplying binomials.
If your child does not understand the way a particular concept is taught in the textbook that can really suck the fun out of the subject. Khan Academy and YouTube are good resources for finding alternative explanations.
Maths also has a reputation for being very black and white. In other words an answer is right or it is wrong. More open ended activities where there isn't necessarily one right answer but more of a focus on the process can help here. Family Math:The Middle School Years has lots of great activities and we also used resources from the North Carolina Department of Public Instruction - just click on the grade level, then instructional resources. The site has been reformatted since I used it but the Maths Stars and Problem Solving Decks look familiar. There's material for highschoolers too. Or try alternatives to the standard approach to basics like multiplication. Here's one approach and here's another.
For some kids, often those who love to read and write, maths can seem like a foreign territory where their preferred language (words) is rarely allowed. Make sure you continue to use living books. One year I took the series Mathematicians are People Too plus it's sequel. I marked the birthdays of all the mathematicians on our calendar plus found an activity or two to go along with it e.g. we made and used a set of Napier's Bones on 4 April (the death day of John Napier since we couldn't find an exact day for his birth). One another occasion we read The Number Devil aloud and did an activity or two at the end of every chapter. Sadly the site I found a complete set of activities for the book no longer exists but a quick Google search will turn up plenty of options. Anything by Theoni Pappas is sure to be good .Her Mathematics Calendar or Math-A-Day book could fit into a Morning Time routine, or you could try Math Talk at Poetry Teatime. Consider a maths journal where they can write about concepts as they learn them. Or perhaps have your child orally teach a lesson to you.
And don't forget to extend your child if maths is their thing. One approach is to skip grades or move through grade level material. Another approach is to supplement with extension material. The University of Waterloo's Problem of the Week was one resource that we used.
In a nutshell don't just rely on a maths textbook when your children get older. Certainly use one if you want or need to. I definitely did. But don't be a slave to it. Feel free to still use games, living books and hands-on manipulatives. Switch up the instructional material and method - at least occasionally. Provide some real life examples, not to mention extra challenges to those who are looking for it. Both math lovers and math haters will thank you.