"We accept all students for who they are; their heritage and what they can bring to the school," he said.
"We constantly find that students' own experiences contribute to learning, particularly in the arts subjects.
"If students are learning about something in social studies, history or geography that's relevant to a student from a particular background, we encourage them to contribute to the class."
Students were also encouraged to use their experiences for assessment.
"They might, for example, do a speech related to something from where they're from," Mr Shanahan said.
"It can be a great experience for students who have always lived in New Zealand as well, because they get to learn first-hand about different cultures."
Waitakere College has 80 teachers and 40 additional staff working with the 1300 students at the school.
At least 40 members of staff are immigrants, Mr Shanahan said.
"We try to have a diverse range of staff to relate to the diverse range of students.
"They can explain things to students which other staff members might not be able to and can help diffuse situations."
Students are able to learn Mandarin, Japanese, Maori, French and Samoan.
There are also occasional opportunities for students to go on overseas trips.
"Diversity is a part of everything we do.
"We have lots of groups outside of the classroom as well; the traditional ones, but also an Indian club, an African club and a Filipino club."
The school acknowledges the different backgrounds by putting a flag up in the assembly hall for every new international student who comes to the school.
The five-year tradition has led to more than 70 flags being raised so far.
