A new proposal by Sen. Elizabeth Warren of Massachusetts to fund universal child care takes its inspiration from the success of the Head Start and military child care programs. While appealing in theory, replicating either of these systems is fraught with challenges.

I would know. I helped create the military system and later oversaw Head Start.

A viable national solution should focus on the underlying principles we used to improve quality and access in both systems. Critically, in both cases, we started with an acknowledgment of what already existed and a clear vision of what needed to change and built up from there.

A federal-to-local program based on the military and Head Start models, like the one Warren proposes, misses the reality of child care in America. Bypassing the states could destabilize existing programs and, more important, upend the parent choice that underpins the current system and benefits very young children.

To the outsider, the military model appears to be federal-to-local, but its success hinges on the installation commanders, with oversight from major commands and military branches.

That structure isn’t easily reproduced elsewhere. Even with the Head Start model, federal regional offices play a significant role in managing the grants to local providers. Congress itself has struggled with integrating Head Start programs into existing state and local systems, and created Head Start Collaboration offices to improve this.

Both designs are guided by the principle that all children served deserve quality, especially when public funds are used. That required clear and achievable standards and paths to quality as defined by national accreditation.

Very early on, Head Start set performance standards that could be measured. When we established the military standards in 1988, they were set at the median of the state standards at the time.

Enforcement of standards was a core requirement from the inception of both programs. Inspections were mandatory and comprehensive, with a multi-level system of checks and balances.

The third major factor is the workforce. In both cases, the goal was to improve the knowledge and competence of the existing workforce. Both used the Child Development Associate credential as the first goal for staff and created ways for those already working in the programs to reach it. Training is consistent, free, offered onsite and leads to higher pay. To this day, the military model is based on a mix of staff with college degrees and those who meet the credential requirements.

Parents and children need options. Not all children thrive in a center-based program. Family child care is a solution for many parents, and both programs provide choice while insisting on equivalent training, standards and oversight.

Nearly ignored in the current debate, to my chagrin, is the role of parents. The military system was built on the concept that child care is a shared responsibility between parents and the Defense Department.

The last lesson from the military and Head Start models is to understand the need and accurately project the cost to meet it. Nationally, we still lack comparable reliable data on the scope of the child care need and what it will cost to improve the current system while expanding to serve more children.

If, as a nation, we decide this is a goal worth pursuing, we have a long way to go to achieve it. We must learn from what works, but when it comes to caring for children, one size truly does not fit all.

Linda Smith is director of the Bipartisan Policy Center’s Early Childhood Initiative.