A series of co-ordinated bomb threats sent to school across NSW on Friday appeared to coincide with hundreds of threats sent to schools around the world.

At least five NSW schools received the same pre-recorded telephone message between 10.50am and 11.10am on Friday, advising that there was a bomb on school grounds.

Students were evacuated and police conducted sweeps at Penrith High School, St Monica's Primary School in Richmond, Woolooware High School, Lake Illawarra High School and Mona Vale Primary School but nothing suspicious was found.

Schools in Melbourne and Phillip Island received similar threatening phone messages. On Friday afternoon, Sydney time, dozens of schools in Hawaii and Delaware were also targeted.