Improving teacher pay and district funding would do basically nothing to help population growth. There are probably fewer than 50k teachers in Mississippi. Even if every teacher with an alternative certification was pushed out of school be degreed teachers that otherwise would have lived in another state, that won't move the needle.
For school spending, there are probably some schools that would be better with more spending, but most of our good schools aren't good and bad schools aren't bad because of the amount of money they do or don't have. It's all basically SES of the students' families and to a lesser extent, the community at large.
Universal preschool, if we did it in a way that reasonably affluent people felt comfortable sending their kids there (spoiler, we won't do it that way), would be a huge boon to working families with young kids. Not sure if it would move the population needle though because I don't think many people are going to plan around that. Even if you have three kids, paid preschool would cover at most 6 years of daycare costs. Pretty significant, but not something most people are going to be thinking about when they select a place to live.
If we went big on universal school choice with a voucher system, it would at least make Jackson affordable and practical (assuming reliable water and trash service eventually comes back) for families to live there. It would make a lot of Mississippi with poor public schools much more desirable. Give a chance to places like the Delta where they don't have a lot of jobs that can support paying for private school for multiple children.
Improving teacher pay and district funding may not immediately help population growth, but those are two(of many) drivers of population growth/decline so its pretty absurd to argue against them, given reality.
Higher pay helps attract more talent.
Higher pay helps retain talent.
Higher pay helps incentivize going to an area that one may not otherwise consider.
More district funding gives students more personalized learning opportunities.
More district funding allows more infrastructure improvements.
These things, and more, are what make a district or state school system attractive to people on the outside looking in.
This isnt some quick fix, and I said as much when I mentioned it will look better over a generation.
Universal preschool has been shown to close the gap between the have and have not kids. The earlier kids can get into school and learn all those evil SEL skills that help create nice people(manners, how to express frustration in a healthy way, patience, responsible decision making, build relationships, etc), the better off kids are as they advance in grades. This absolutely will help population in the long term because more prepared students can make a school district more attractive to enter into or stay in. Again- outside looking in. Further, those students will become parents and if they see they had a complete education and have turned out well, they are more likely to seek out such an education for their kids...which means they stay in state. Better behaving kids who turn into better educated and adjusted adults that in turn send their kids to similar schools also makes for a better workforce. This means more jobs.
All this is connected and while there is no single magic fix, since everything is connected, one thing can help improve other issues.
As for a voucher system- Public tax funding should not pay for schools that can turn students away due to physical or mental limitations. Public tax funding should not pay for schools that can turn away students due to beliefs. Public tax funding should not pay for schools where there is no oversight into how the funding is spent.
If private schools are willing to take on the financial cost of educating everyone, are willing to accept all students regardless of belief, and are willing to follow established procurement procedures and be audited, then cool- voucher away.