We had the same rules as MidWestMom - if the kid had a fever or was throwing up, they stayed home form school. Chances were, the school would call me anyway.
Where this backfired, was when difficult child 3's anxiety got so extreme that it actually made him spike a low-grade fever, he would feel nauseous and often throw up. Sometimes he'd be fine in the morning, a little nausea but no fever. I'd send him to school (and he wanted to go to school) then I'd get a phone call an hour later to come and get him.
At the time, his class teacher was insistent that difficult child 3 had some serious and undiagnosed physical illness that we had to investigate. She said she would watch him change colour and suddenly really look sick.
We investigated everything, searching for a physical cause. We tried checking for food sensitivity (which can be a factor in 30% of Autism Spectrum Disorders (ASD), we were told). That was tedious and time-consuming. He lost weight on the elimination diet, but we still couldn't pinpoint symptoms, which never really went away even on the elimination diet.
He was investigated for ulcers and Helicobacter infection. I can't remember everything that was done, most of it non-invasive.
Still the problems happened. I had to see doctors myself, but I could never be certain I wouldn't get a phone call to come fetch him, while I was on the way to my own doctor, so I took to bringing difficult child 3 with me on my appointments rather than risk having to keep cancelling.
I could see the correlation with school and the symptoms, but I really didn't think anxiety alone would cause a fever to spike. That one threw me.
Over the school year, difficult child 3 would have missed about half of it. The truant people were sniffing around, the principal was supportive and headed them off (he knew difficult child 3 wanted to be at school but was always sick). We staggered our way to the end of the school year with difficult child 3 doing most of his schoolwork at home.
And that is another thing - I didn't want staying home to be a reward, even subconsciously. So we had a rule - school work during school hours. If you're home sick, and you're too sick to work, you can sleep. It's okay. But if you're feeling well enough to sit up in bed, son, then here's a lap desk, your work sheets and a pencil. Go to it, I'll be in with a snack for you.
We had educational software on the computer which he was allowed to use as a break and a reward. "Yes, you can be on the computer, but it's school hours so you can only do educational games."
One thing I learned that year - difficult child 3, despite having been taught (and I had seen the assessment tasks come home and helped him put them together) had no knowledge of Geography. We went on a driving holiday and he kept asking if we had left Australia yet. I got the globe down from the shelf and asked him to show me where Australia is. He couldn't do it. Nor could he identify any other land mass.
So one game I let him play when he was home, sometimes all day, was "Where in the World is Carmen Sandiego?"
In two months he learned more Geography than he ever had before. He's also retained it and built on it - when he saw an item on the news about Japan, for instance, he now knew where it was and had a mental picture of what it is like there.
End result of all this - we were getting ready for school the following year. There had been no fever and no nausea all holidays. Then we were going to a family birthday party at the museum - difficult child 3's favourite place - the week before school was due to go back. difficult child 3 said to me, "This year at school I will ignore the bullies and walk away."
I said, "That is a good strategy. Also you can tell a grown-up, the bullies are not allowed to be mean at your school."
He nodded happily. But within fifteen minutes, he was throwing up.
That convinced me - we'd found no physical cause for his illness. He'd been well for months. And now, at the first mention of school, the symptoms were back in full.
We sent him to school as usual. Different teacher, different class. But he was very quickly not coping, so I changed schools. The new school was much more vigilant at protecting difficult child 3 from bullying, but by this time he was highly reactive. His anxiety was extreme and there were a couple of incidents which the school handled with sensitivity, but which showed me that for difficult child 3, we'd reached the end of the road with mainstream education. When the nausea and fever began again, I pulled him out.
It was a lot easier having difficult child 3 at home - at least I would not get my day disrupted by having to go fetch a vomiting feverish kid from school. Now at least I knew what I would be dealing with. If I had to do the grocery shopping, difficult child 3 came too. I gave him the shopping list and would ask him to find me the most economical baked beans, for example. I got him to help at the checkout. He helped with transactions and got to know the procedure of how to interact with shop staff. He then took this further - he wanted a toy, he'd saved up for it, so he went shopping for it. He went to several shops, found out how much they charged, asked if they would price-match, then talked them down for the best deal. I was delighted.
At school, kids have to spend time with (and get on with) a group of others the same age as them, with a wide range of abilities. The social interactions are therefore not representative of the more commonly found cross-section of society. School is an unnatural social environment. True, kids learn social skills, but the social skills they learn at school, interacting as children with other children, are not the same social skills we use as adults to interact with a wider range of humanity. Autistic kids especially can struggle with this - learn one set of social skills at school then have to unlearn/relearn when you leave school and get a job.
For difficult child 3, he learned what he will use most in life - to get on with everybody, to deal with the full cross-section. Old, young, frail, robust, female, male, infant, geriatric. Staff, customers. Friends, strangers.
He's still a work in progress, but it's been much better progress since leaving face to face teaching.
We enrolled him in a correspondence school which did also give some opportunity for face to face interaction (about one day a month on average). We could also take him to the school for a face to face lesson. We did that a lot. Again, it helped him. His anxiety reduced and over time, he became less reactive.
Whatever you do for your son, you will need to get his anxiety under control or it will just keep escalating and have his school attendance erratic and unpredictable. You can either try to eliminate the cause of his anxiety (if that is possible, and you can identify it) or remove him from the environment causing the anxiety. Over time he could well learn to manage his own anxiety. difficult child 3 can't tolerate anti-anxiety medications, so that was not an option for us. He's finally learned to recognise his symptoms and rationalise, as far as possible, to resolve them. He's still got a way to go, but every time he succeeds and pushes through, is a win that reinforces that he can do it.
I hope this can help you in some way. Just remember - this is real, this is not just a wimpy kid. Chances are, he's one of the bravest people you've ever known.
Marg