Reagan High School in San Antonio has a reputation as the premier high school in the North East Independent School District, and that has led to severe crowding. The burden of too many students in not enough space is beginning to show. Counting more than 300 employees, nearly 4,000 people make their way onto Reagan's campus every weekday. When the bell rings, teenagers spill out of classrooms, clogging corridors and stairways and bouncing off one another like pinballs. Built in 1999 to hold no more than 3,000, enrollment has fluctuated this year from 3,500 to 3,650. The crowding is pushing class size to 30 or more students.