School districts in the Washington area are revamping their truancy policies in an effort to keep in school the thousands of students for whom attending class simply is too onerous.

In the District, where an estimated 20 percent of all students are truant, a policy passed in late August by the city’s school board includes extending to 25 the number of unexcused absences a student must accumulate before referral to the city’s juvenile-justice authorities. Previously, the threshold was 15 days, but officials said the policy was neither effective nor evenly enforced.