I substitute taught like many of you. Especially when I was moving and new to a city, substitute teaching was a flexible job option. I wanted to share about substitute hiring agencies and my experience using them.
A lot of charter schools struggle filling the demand for substitute teachers. A lot of them may end up hiring an "in-house" full-time substitute teacher, but it was quite common for me to see substitute teachers being outsource through these agencies like Scoot. The benefit of working for agencies is that there really is no full-time commitment. It's genuinely work as you need which was huge for me at the time.
They used a popular app that many substitute teachers used to view available jobs and it was a first come first serve basis. They had control over which assignments were offered to you, but it was pretty much automated and based on your preferences when you sign up. Like what grade, what subjects, and what time span were some options. They also had a phone bot that would remind you of sub days or also call you whenever a job opened up.
Something to consider is that this also means you may not get work for quite a bit. You will definitely many times not have full-time worth of work. So this is really more of a very flexible part-time gig.
If you're trying to use this to get a full-time job, you can for sure. The benefit is you can meet a variety of schools rather than be stuck at one. The key is to really be helpful as possible, and meet as many teachers you can in the break room. Look for the ones that are friendly and seem like they would like to talk to you. Most may be uncomfortable to talk to you at first, mainly because of liability and privacy concerns since you are not a permanent employee, but if you're lucky they will open up and even put in a good word for you. This happened to me multiple times. Don't bother teachers that don't want to talk to you though!
Another downside is that you'll be getting the most difficult assignments more often than not. I noticed the schools I wanted to work for were almost never called for or only used full-time substitutes.
End of the day, start with this, and definitely apply for full-time sub positions in the schools you want to work for.