Three-quarters of the nation's schools discriminate against pregnant girls and teenage mothers, a study by the Equality Center said Sunday.

The center, a research organization, said more than 300,000 girls 18 years old or younger become mothers each year, and more than 40 percent of all girls who drop out of school give pregnancy or marriage as their reason.The study, entitled "The Need for a Warming Trend," said few schools have clear policies about how to treat pregnant and parenting students and, as a result, schools take actions that violate the federal law that prohibits sex discrimination in schools receiving federal funds.

Margaret Nash, project associate, said common school practices that are illegal include not allowing excused absences from school for problems associated with pregnancy, birth or child care, not reinstating students to the status they held before leaving for pregnancy and not allowing pregnant and parenting students to be club or class officers, or student government representatives.

"The school climate - measured by school policies and practices as well as staff attitudes - is chilly for pregnant and parenting teenagers," said the study.

Nash said the study surveyed 12 diverse schools across the country, ranging in size from 450 to more than 7,500 students.

In examinating attitudes of school staff, the study found that pregnant and parenting teens typically are viewed as second-class students.

More than half of the schools report that sometimes teachers think pregnant and parenting students are morally or intellectually inferior and almost half report that teachers or school personnel view pregnant girls and teen mothers more harshly than teen fathers.