Too sick to go to school but not so sick that you can't use the computer? Besides if it was so important to you, why didn't you just go to school. Unless you got aids or something like that.
I hate people who say things like this.
It takes a lot less energy to sit with a Laptop and move a mouse around, than it does to go to school, travel around an entire school, pay attention to a lot, put up with a lot of noise and try to learn. Not to mention, if you go to school sick, you're likely to end up getting other people sick.
If you're also the sort of sick where you may have toilet trouble, you'd rather be in your own house than at school and have to end up going home anyway.
It's also not uncommon to get sick in the sense that you're not totally sick all the time, but have felt sickness in the sense of vomiting, which can come on at any time during the day.
Using a computer while sick is the sort of thing you do to cure boredom, especially if you're too sick to go to school, but not so sick that all you can do is sleep.