I'm pretty familiar with this problem space having worked in both a state department of education and a school district.
I would not expect this to be a long term success. Virtually every district of reasonable size starts with a homegrown and maintained solution and ends up going with one of the big guys for lots of reasons.
1. Security/liability. You have to have pretty damn good systems here and definitely want to point at someone else's assurances and contract that allows for recourse.
2. Rapidly changing business requirements. This is everything from state and federal reporting requirements to the expectations of end users. It's hard enough to maintain these core systems and keep folks around who are good enough to do it. Now deal with changing technology (oh you want a parent portal? Oh, you don't want to use Flash/Java for iPads? Oh you want ...) and you really can't attract and retain the kind of software people you'd want to continually redesign, refactor, rebuild, extend, and expand. Development on these systems never stops, which is why it's often easier to just drop off the old and buy the new hotness. It's also why scale is so helpful with these systems. If your users want this, someone else already requested it or will shortly. A lot of the improvements in these systems happen because of how many users they have and can be made because the cost is spread across all those users.
3. Interoperability with other systems. Most of these systems are not omnibus catchall solutions for the entire business needs of a school district. That's probably for the better-- the folks who try to do that end up doing it very poorly. But you will want your HR and payroll to talk to your student information system that should probably talk to your assessment system that should talk to your curriculum management system that should talk to your special education IEP case load management system, etc. It's hard to do this and even harder when your solution is built to work in one context. Standards here have only barely helped. Middleware is expensive, shitty work. Again, not easy to attract killer talent and it is a constant need. The big boys have everything else built and just focus on middleware and have probably already worked with and written what's required for all of the popular systems you are using in these other areas.
This is just the smallest fraction of reasons it's a huge PITA to write and maintain these systems. That's not to say that it can't be done but it is to say that this is not a small, well-defined problem space with just a few distinct end-user types and functional requirements that can be built once and then monitored and tweaked over time. Not if you want to do the real stuff that makes collecting and maintaining all of this data worthwhile.