As of the 2000 census, there were 29,644 people, 10,622 households, and 8,178 families residing in the town. The population density was 4,403.1 people per square mile (1,700.7/km²). There were 10,819 housing units at an average density of 1,607.0/sq mi (620.7/km²). The racial makeup of the town was 89.98% White, 3.88% African American, 0.09% Native American, 4.08% Asian, 0.01% Pacific Islander, 0.62% from other races, and 1.33% from two or more races. Hispanic or Latino of any race were 2.82% of the population.
There were 10,622 households out of which 40.8% had children under the age of 18 living with them, 68.0% were married couples living together, 7.1% had a female householder with no husband present, and 23.0% were non-families. 19.3% of all households were made up of individuals and 9.4% had someone living alone who was 65 years of age or older. The average household size was 2.77 and the average family size was 3.20.
In the town the population was spread out with 28.4% under the age of 18, 4.0% from 18 to 24, 29.6% from 25 to 44, 24.5% from 45 to 64, and 13.5% who were 65 years of age or older. The median age was 39 years. For every 100 females there were 92.1 males. For every 100 females age 18 and over, there were 87.4 males.
According to a 2007 estimate, the median income for a household in the town was $120,978, and the median income for a family was $146,891. Males had a median income of $82,420 versus $45,305 for females. The per capita income for the town was $47,187.
Students in Kindergarten through 12th grade attend the Westfield Public Schools. The district has six K - 5 elementary schools and two grade 6 - 8 middle schools, which are divided by a "North Side / South Side" boundary. The schools in the district (with 2005-06 enrollment data from the National Center for Education Statistics) are as follows:
The public schools on the north side consist of Franklin Elementary School with 592 students, Washington Elementary School with 348 students, Wilson Elementary School with 582 students and Theodore Roosevelt Intermediate School with 721 students.
Schools on the south side are Jefferson Elementary School with 491 students, McKinley Elementary School with 334 students, Tamaques Elementary School with 468 students and Thomas Alva Edison Intermediate School with 719 students. Thomas Alva Edison Intermediate School is noted for its excellence in academics, activities, and the arts.
Students on each side of town are divided amongst the three elementary schools on their side, go to a common intermediate school, and then join the other side of town in Westfield High School, which has 1,769 students in grades 9 - 12. The sides of town are divided into North side and South side, and they are divided by the train track for the New Jersey Transit Raritan Line that runs directly through town.
Starting in the 2008/2009 school year, all kindergarten classes in the school district were centered at Lincoln School on the south side of town.
There is also a Middle States accredited Catholic school, Holy Trinity Interparochial School, run by the three parishes of Holy Trinity in Westfield, St. Helen's in Westfield and Our Lady of Lourdes in Mountainside, which offers education from Pre-Kindergarten to 8th grade.