What's the alternative to building a citywide data system?

In my last post I raised the possibility that, if ARIS data is flawed, the city records that ARIS is built on could also be flawed. A reader just e-mailed in this response:

Agreed that this could be a big concern – but wouldn’t it be great to get out there that having the data easily accessible to teachers – which has not been the case — is an opportunity for schools to fix that and give teachers the accurate data that they need to provide students with effective instruction?   Not on the scale of sweeping social change, but a huge step toward school improvement, no?  What’s the alternative – we give up on data entirely?  Start over, but without the historical data for kids already in the system?