WASHINGTON (AP) — Democratic presidential candidate Kamala Harris on Saturday called for a significant federal investment in teacher pay, the first policy proposal that she has put forth since officially launching her 2020 campaign.

At a rally in Houston, Harris argued that the U.S. faces a teacher pay crisis that requires a national response. She pledged by the end of her first term to close a pay gap that Harris said currently amounts to teachers making about $13,000 a year less than other college graduates.

"You can judge a society by the way it treats its children, and one of the greatest expressions of love that a society can give to its children is educating those children with resources they need," Harris said.

Harris' campaign is citing a study from the liberal-leaning Economic Policy Institute that found that what's called the "teacher pay penalty" — the difference in compensation for teachers and comparable public workers — is larger than ever. The Economic Policy Institute study puts the teacher compensation penalty at a record-high 11.1 percent in 2017.

Harris, a U.S. senator from California, plans to release more details of the plan next week, but she said her proposal will amount to the largest federal investment in teacher pay in American history. It was not immediately clear how much money Harris is calling to be diverted to educators' pay or how the plan will be funded, but she told a packed gymnasium at Texas Southern University that the cost shouldn't be the question.

"The question is: What's the return on the investment?" Harris said.

Harris' focus on the pay of educators comes as walkouts by teachers protesting low pay and education funding shortfalls have made headlines across the country. Throngs of teachers have marched in states across the country demanding better funding, including in California.

In February, Harris threw her support behind striking teachers in her hometown of Oakland, where she launched her campaign earlier this year.

The rally in Houston was Harris' first in Texas since announcing that she would seek the Democratic presidential nomination.

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Associated Press Writer Paul J. Weber in Houston contributed to this report.