Graham School in Scarborough was searched by police yesterday after a suspicious email was received.
One senior police advised that the school remained open and police teams carried out their search after pupils had gone home on Monday.
The all-clear was given following a thorough search and the school will be open as usual today.
Headteacher Paul Brockwell said: "The safety of our students and our staff is paramount and we liaised closely with the police.
"Their advice was that there was no need to close today and, following the search, we will be open as usual."
The school was closed on two days last term after suspicious email were sent to the school.