Marking a new chapter in education philanthropy, the Bill & Melinda Gates Foundation will step back from its traditional education reform agenda to instead invest close to $1.7 billion over the next five years on new initiatives that include a focus on building networks of schools.

"Education is, without a doubt, one of the most challenging areas we invest in as a foundation," Bill Gates is expected to say Thursday during a speech at the Council of the Great City Schools' annual conference in Cleveland, according to prepared remarks. "But I'm excited about the shift in our work and the focus on partnering with networks of schools."

In a sprawling address, the Microsoft co-founder and co-chair of one of the most influential and contentious entities involved in the education space plans to reflect on lessons learned about the foundation's efforts and how those lessons will play into its revamped vision for the future.

"There are some signs of progress," Gates is expected to say of past efforts. "But like many of you, we want to see faster and lasting change in student achievement."

During the Gates Foundation's involvement in education philanthropy over nearly two decades, the organization – of which Bill Gates' wife, Melinda Gates, is also a co-chair – has poured billions of dollars into advancing new ideas and played an especially significant role in the rise of the education reform movement. Yet it has been widely criticized for funneling funding into what some consider silver-bullet policies or the latest education fad.

One of the foundation's first serious forays into K-12 policy was its push for smaller schools – a contentious idea that yielded mixed results.

While it had a positive impact in some places – such as New York City, where graduation and college enrollment rates increased for the majority of smaller-scale schools – it didn't move the needle in many other places and ultimately was deemed too costly, both fiscally and politically, to replicate successfully.

The foundation's biggest bets, however, were in its decision to back the Common Core State Standards – academic benchmarks for what students should know by the end of each grade – and its push to reimagine teacher evaluation and compensation systems based in part on student test scores.

That effort dovetailed with the Obama administration's competitive education grant program, Race to the Top, which gave states hundreds of millions of dollars to carry out those very education policy changes, among others. The Gates Foundation was instrumental in helping states that won the funding but lacked the capacity and expertise to go it alone and carry out their winning proposals.

The results of those efforts, however, also were mixed.

The District of Columbia, for example, is hailed by many education policy experts as a model for how school districts can create evaluation systems that retain and reward the best teachers while showing the least effective ones the door. But some states, like Tennessee, have had a harder time sticking to their original visions, largely due to the politicization of Common Core, which led to a chain reaction in how states were able to test students and make the results of those tests part of teacher evaluations and pay scales.

In May 2016, Sue Desmond-Hellmann, CEO of the Gates Foundation, offered somewhat of a mea culpa for the foundation's misread of how ready – or not ready, as it turned out – states were to handle implementation of the Common Core standards.

"Unfortunately, our foundation underestimated the level of resources and support required for our public education systems to be well-equipped to implement the standards," Desmond-Hellmann wrote in an open letter. "We missed an early opportunity to sufficiently engage educators – particularly teachers – but also parents and communities so that the benefits of the standards could take flight from the beginning."

Gates is expected to use Thursday's speech in part to echo that sentiment, as he plans to say "it became clear that teacher evaluation is one important piece of several critical elements." Of the Common Core standards, he will say "more needs to be done to fully realize their potential."

He also will emphasize what the foundation will prioritize in the future. Going forward, Gates is expected to say, the foundation will no longer invest in new initiatives designed to tackle teacher evaluation and compensation, although it will continue to collect data on the effectiveness of its previous efforts. Instead, it plans to increase funding for curriculum design and professional development aligned to states' standards – be they the Common Core or others – and also continue its support for charter schools, though it will tailor that focus to schools that are improving outcomes for students with disabilities.

According to Gates, about 60 percent of the new $1.7 billion investment will support the development of new curricula and the foundation's new venture centered around building networks of existing schools, and about 15 percent will support the foundation's charter school work. The other 25 percent will focus on "big bets," which Gates characterizes as having "the potential to change the trajectory of public education over the next 10 to 15 years."

The foundation's vision for building school networks includes funding up to 30 networks, beginning with a focus on high-needs schools and districts in six to eight states where data collection and analysis is used to drive results, particularly when it comes to closing the achievement gap between students of color and low-income students and their white and wealthier peers.

"We will focus on locally driven solutions identified by networks of schools, and support their efforts to use data-driven continuous learning and evidence-based interventions to improve student achievement," Gates will say, underscoring a recent sea change in the foundation's recognition that local community buy-in is essential for the success of most education policies.

"We will leave it up to each network to decide what approaches they believe will work best to address their biggest challenges," Gates is expected to say. "Giving schools and districts more flexibility is more likely to lead to solutions that fit the needs of local communities and are potentially replicable elsewhere."

According to the prepared remarks, Gates additionally will outline what the foundation envisions for these networks by citing already-existing partnerships.

Examples he'll share include: the Network for College Success, a group of 15 schools that have partnered with the University of Chicago and in which researchers help educators keep tabs on a set of indicators predictive of student graduation and college enrollment; California's CORE Districts, which involves a group of school districts that banded together in 2010 to help each other implement the Common Core and more effective teacher training programs; and Tennessee's Lift Education, which brings together superintendents from rural and urban districts across the state to collaborate on best practices.

"We believe this kind of approach – where groups of schools have the flexibility to propose the set of approaches they want – will lead to more impactful and durable systemic change that is attractive enough to be widely adopted by other schools," Gates will say.

Over the next 30 to 60 days, the foundation plans to gauge interest from nonprofits and other education organizations about leading school networks, and to gather information about their experience and capacity to do so. Working with chosen intermediaries, the foundation eventually will begin looking at specific schools to participate in its networking effort.