Thousands of students nationwide marched in the streets or rallied in public parks, at state capitols, and in other locations in response to the legislation pending in Congress that would significantly tighten enforcement of immigration laws. Some of the largest demonstrations were in California and Texas, but students have also rallied in Arizona, Nebraska, Virginia, and elsewhere across the country. As waves of students staged walkouts and joined protests over proposed punitive changes to federal immigration law, school administrators sought a balance between allowing students to demonstrate peacefully and setting clear expectations that they should return to class soon. Some school leaders said the events were the largest and most quickly organized protests among precollegiate students they could remember. Several principals and superintendents admitted to being taken aback by what they described as an unusually forceful display of civic activism among their students. (Contains 1 photograph.)