I'm going to let you in a secret that many teachers in my building share. I hate calling in sick. I go into work if I can help it. Why? Because making sub work is more work than just going into work. Not only that, if you don't get a sub that you are familiar with, it's a huge crap shoot on who you could end up with. I learned this lesson while I was student teaching.
See, even though I was teaching all of the classes, my cooperating teacher still had to call in a sub if she was sick. Sometimes they were relieved to sit in the corner and read a book while I did their job. Other times they refused to let me have control of the class. And then, there were the crazy people.
There were two subs that I had while student teaching who I would never let into my classroom. One was an older woman whose daughter was an elementary teacher. She retired from her own job and thought she'd take up substituting to kill her boredom. She was surprised to find me waiting in the room for her. I explained the lesson I had prepared and said she could participate or sit back, whichever made her more comfortable. She looked at me with condescending gaze and said "But I brought puzzles and crayons for the kids." Bare in mind, these were seniors and this was about a month before their massively important portfolio was due. When I insisted that we follow my lesson, she said "I went to the trouble to get these puzzles and crayons together. I think you can at least let them try the activity!" I told her I'd let the kids vote. They voted for my lesson because they knew they were going to do it anyway. And my lesson involved group work, which they loved. She sat in the corner of the room pouting the entire day because I was so mean as to make my students do actual work.
The second sub was about my age. He showed up with a guitar. To my horror, he intended to use it. This was when the huge portfolios were due in two weeks. We were actually in the lab revising our pieces for the portfolio. I turn around and he's singing a rap song, with guitar accompaniment, about God knows what. I told him he needed to stop because the kids were distracted. Then I noticed he was awfully quiet and I couldn't find him. Come to find out he was sitting down at one of the computers in the middle of a group of kids telling them that the portfolio is just another way for the "man" to keep them down and they should quit working on it immediately. Many of the boys in the class also disliked him and made it known. When I asked them why the next day, they told me they didn't like him "spinning game" on their teacher. Aw. My kids were being protective. They also told me they were pretty sure he was high. I told the front office that he really shouldn't be allowed to sub in the building again.
Subs come in all shapes and sizes. The two I've shared are awful, but that's not how all subs are. My favorite subs can come in, work a lesson and leave you detailed notes on how the lesson worked and which kids participated. Some subs leave the building in tears. I've joked that students can smell fear, but it's definitely true. If you want their respect, you need to project confidence and respect for them.
The horror of who could end up in my classroom isn't the main reason that I dislike calling in, though. No. It's because I hate having to write out exactly how my lessons go through the day. It's much easier if I just do it myself. That combined with ending up with a crazy dude with his guitar or some lady that insists your kids really need to do puzzles instead can really ruin your plans for the rest of the week.