If it’s Monday, it must be another giant spending proposal from one of the Democratic presidential candidates. This week, like most weeks, the winner is front-runner Elizabeth Warren, who called in a post on Medium for another $800 billion in federal spending on K-12 education.

Her “plan”—she loves that word—would quadruple current spending on Title I funds for schools with low-income students to $450 billion over 10 years. She also wants $200 billion more for students with disabilities, $100 billion in other grants, and $50...