[4] He came out to the faculty during a meeting of the Committee on Human Differences at the school in response to a colleague's statements that "homosexuality wasn't an issue at Newton South" and in "20 years of teaching he had never encountered a single gay student.

He said: “It would have helped enormously if I’d had even one openly gay teacher in high school to serve as a role model.” He subsequently started the Gay-Straight Alliance at Newton South.

Hundreds of them -- gay and lesbian, as well as heterosexual -- wrote letters to their legislators, staged rallies and candlelight vigils at the State House and met personally with all 40 Senators, or their aides."

[2] Parlin came out to his students every year, and spoke on subjects such as homophobia during the school's annual Transgender, Bisexual, Gay and Lesbian Awareness Day.

[10][11] In addition to his involvement with other organizations related to LGBTQ+ rights, he was a founding member of the Cambridge GLBT Commission [12] and prominently advocated for legislation that allowed gay or unmarried heterosexual couples to register as domestic partners and thus be eligible for bereavement, health insurance and pension benefits.