Aren't we allowed to get sick?

As employees there are numerous rules and regulations to follow in our different professions. At times it feels as though we are being dictated by our employers. We are monitored in whatever we do which is understandable. We get paid to perform certain tasks for a predetermined period of time and our managers are tasked to insure that we stick to our work. This doesn't bother me. What bothers me is when our personal lives are being dictated also.

We're sometimes faced with circumstances that are beyond our control to which we need to attend to. There might be an emergency at home requiring your specific attention and you might need to leave work early or not attend at all. When this happens you'll need to provide proof. How does one provide proof of a child having an emotional reaction towards a relative being ill? The child is crying and cannot attend school because they love their aunt, uncle, grandma or grandpa. It's only you that can calm the child down or you're the only one available at the time. What proof would this require?

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I fell sick in February for a week and I couldn't go work. I got a doctor's note and recommendation for the sick leave. This is causing quite an issue with my employer. After I had submitted my sick note, I received some forms to fill out a few weeks later. These forms are for short term incapacity leave. This kind of leave can get messy. The employer could choose to accept or reject it and thus cause me leave without pay for those days which is quite a lot of money. What was the point of going to the doctor and being recommended for leave to recover from my illness if it might be rejected? What would the rejection mean exactly? That according to them I wasn't sick and stayed at home for fun? Or that it's not their concern that I fell ill? Or that I'm not suppose to get sick? I'm finding this quite perplexing.
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Today I spent about an hour in my principal's office being basically told not to get sick again. The principal and I were busy going through the incapacity leave forms as she was telling me this. I was quite confused. How is my falling sick in anyway by choice? I can't control such things, It's nature. I understand that being away from work for such a long time is concerning but I had a good reason and provided proof that was needed so I don't understand what the issue is. We are human, not machines. Why should we be told when to get sick and when not to? When has work priority before our families and our health?

Perhaps the lack of experience is rendering me naive and a bit brash but this really doesn't make sense. I enjoy my work. I love working with my learners. The office politics of the job is what irritate me about being a teacher. I try my level best each and everyday to be good at what I do. I go beyond the call of duties more times than I care to admit. Why can't such efforts be recommended as much as the undesirable things are pointed out? There should be a balance.

Please share your own unpleasant work experiences you've had and how you dealt with it.If you're an experienced teacher and a principal could you advice me on this matter?