Some children—such as those who didn’t attend a high-quality preschool program, who are dual-language learners, or who are less developmentally ready—may need additional supports.

While most state-run programs do have policies in place to support young ELLs, the guidelines vary widely in quantity and quality, a new National Institute for Early Education Research report found.

In San Antonio’s Harlandale school district, pre-kindergarten students learn English and Spanish together. They help one another through instructions and assist each other in the language they ...