Formal “hit the road” departure ceremonies are unusual but growing in popularity, said Joyce Holl, head of the National Orientation Directors Association. A more common approach is for colleges to introduce blunt language into drop-off schedules specifying the hour for last hugs. As of 5:30 p.m. on Sept. 11, for example, the parents of Princeton freshmen learn from the move-in schedule, “subsequent orientation events are intended for students only.”

The language was added in recent years to draw a clear line, said Thomas Dunne, the associate dean of undergraduates. “It’s easy for students to point to this notation and say, ‘Hey, Mom, I think you’re supposed to be gone now,’ ” he said. “It’s obviously a hard conversation for students to have with parents.”

For evidence, consider a chat-board thread by new Princeton parents on the Web site College Confidential. “Do parents hang around for a day or two after orientation in case their kids need something?” one poster, mrscollege, asked. “I say no, but we have a friend who is planning to hang around for a while in Princeton for her son just in case.”

Some undergraduate officials see in parents’ separation anxieties evidence of the excesses of modern child-rearing. “A good deal of it has to do with the evolution of overinvolvement in our students’ lives,” said Mr. Dougharty of Grinnell. “These are the baby-on-board parents, highly invested in their students’ success. They do a lot of living vicariously, and this is one manifestation of that.”

He and other student-life officials encourage parents to detach — not just at drop-off but throughout the freshman year, including limiting phone calls and text messages.

Parents, of course, know that in their head. But they still struggle to let go.

After lunch on Saturday at Grinnell, before the hail and farewell ceremony, Gary and Glorialynn Calderon easily welled up while visiting the campus mailroom with their daughter. “It’s hard, we’re overprotective,” Mr. Calderon admitted.