Primary school based on the British education system. Located in the Gurney/Pulau Tikus area.
Cambridge International Education based system. This is the international school part of a larger system with other schools around Penang.
Cambridge based education with more Malaysian influence. Tenby International School shares a campus with the Malaysian private school, with both schools together called the Tenby Schools. The wikipedia page for Tenby is interesting, especially if you read down to the Faculty section.
Kuala Lumpur based school with a Penang campus located in Bukit Jambul. International Baccalaureate based education.
Located on the west side of the island, close to Balik Pulau, Prince of Wales opened in 2011. They do have a bus system that picks up students from all over the island, as well as having brand new dormitory facilities for boarding students. Cambridge based education, they are part of the Council of British International Schools.
Kuala Lumpur based school with a Penang campus. Located in the south part of the island, closer to the airport. British curriculum based education and brand new in 2012, they have been offering open houses periodically this year.