Ah, I thought you meant competition for teaching positions. But now that I know what you're talking about, let's sit down for a bit of story time.
Here's what actually happens with "government mandated customers."
There are quite a few states that allow "school choice", and the ones I'm aware of all operate in a roughly similar fashion. There's a "Count Day", usually October 1st or 15th or thereabouts, where the number of students enrolled at that school is counted for funding purposes. However, outside of that day, nothing matters in terms of funding. So, you have private schools who entice students with promises of "a free iPad for every student" and the like. They do whatever they can to get as many students in the door as they can... And then once Count Day is over, they take all the difficult students (disabilities, behavior problems, underperforming) and push them out, whereupon they go back to public schools.
However, at this point, the money for these students has already gone to the private schools instead of the public schools, so now the public schools are dealing with a more difficult group of students while having less funding to do so, while the private school operators rake in the profits (and donate a portion of them to politicians who'll ensure things stay that way).
All this does is to ensure that the public schools get worse.
When you look at "government mandated customers" from the public school perspective, there's plenty they'd rather not have too, but they don't have that option. They are required to take the worst "customers" and still attempt to make them into productive citizens, which is a good thing for all of us, yet "we" fight them every step of the way.
Look, I understand that not all schools are the same. I'm not opposed to the idea of school choice, I'm opposed to the execution that allows private schools to take money away from public schools. I'm opposed to for-profit education taking my tax money and not educating the students they got funded for.