The 10th-grade students were arrested on Dec. 4 and 5 in separate incidents.
A Redondo Beach police investigation found no evidence of planned violence against the school or people there.
The District Attorney's Office did not disclose the exact charges due to the 15-year-old defendants being juveniles. As a precaution, safety measures will continue when students return from winter break next week.
That includes added police presence, several random search days, plus limited entry and exit points.