Guillermo Pomarillo knows the reason he was admitted to Stanford University was because of hard work and not luck. But a recent dental visit forced him to write about his personal struggles in an open letter.

The first-generation college student detailed an interaction with his dentist, who attempted to undercut his accomplishments because of his ethnic and low-income background, in the letter he posted Monday on Facebook.

“Today, I came into your office after leaving work early,” Pomarillo wrote at the beginning of his letter. “Little did you know that I had to walk 1.5 miles to be able to make my appointment. My mother and father couldn’t drive me because they were busy working. But, it was imperative for me to have my teeth cleaned before going to school.”

The Chicago-based student then described in detail how, after he mentioned he would attend Stanford soon, his dentist began to ask him about his ACT scores and made inappropriate comments about his low-income background:

You sarcastically said “Wow you got (blank) on the ACT?! And you got into Stanford?” I was confused, I had always thought my ACT score wasn’t too bad. I mean, I got admitted into many other schools other than Stanny. You then said, “Well my daughter got a 35 and she didn’t get into Stanford. She goes to Umich.” In my head I thought, “Wow that’s great, UMich is a good school.” But you didn’t stop there, you kept going. You said, “Well when you have kids from neighborhoods like THESE, like you know, ENGLEWOOD. It’s easy for them to get into Harvard or Stanford with a (states my score).” In my mind, I was confused. Did he really just say that? But you didn’t stop. You kept going. You said, “You know, when kids go to schools around here. (AKA public schools in minority neighborhoods) It’s easier for them to get into schools like Stanford. My daughter goes to a school where like 20 kids get perfect ACT scores.” I stayed quiet.

But for Pomarillo, who will be studying biomedical engineering at Stanford according to his Facebook, the last straw was when the dentist said he should feel “lucky” to be going to Stanford:

Wait what? So you’re telling me that 18 years of rigorous hard work is like going on The Voice. You’re telling me that pure luck got me admitted into not only Stanford, but schools like Princeton, Vanderbilt, Northwestern, and WASHU, and waitlisted at Tufts, Penn, and Columbia (I didn’t tell him this btw)?! To say that I was admitted into a school simply because of my background is ridiculous. OF COURSE YOUR DAUGHTER WAS GOING TO SCORE HIGHER THAN ME. You’re a dentist that can afford to send her to a school that will help her achieve a score like that. You’re an educated dentist, with a college degree and dentistry degree. My parents, two undocumented immigrants that only obtained a grammar school education, couldn’t afford to send me to private schools. Yes, I may have grown up in a neighborhood that doesn’t have many young kids going to schools like Stanford. But it doesn’t mean that people where I come from don’t have the potential to succeed at Stanford. We deserve to go to places like Stanford.

The student then wrote, “you belittled me... but you were completely ignorant of my struggles,” before he listed the many obstacles he faced growing up being financially disadvantaged while trying to excel academically despite having limited opportunities and resources.

“You are neglecting that I faced more struggles than your daughter. You are neglecting that all odds were against me,” he wrote. “But you feel entitled to say that I got ‘lucky’ and that ‘because of where I come from’ I got into Stanford... Maybe just maybe, the admissions panel saw beyond a score when seeing my profile. It doesn’t mean that I’m better than your daughter. It means that I have the strength, the determination, the perseverance to succeed in a place like Stanford.”

College admissions based on affirmative action policies have long been used to give diverse and low-income students the opportunity to reach their potential at prestigious universities. And, according to Stanford’s website, the university is committed to affirmative action goals.

In June, the U.S. Supreme Court also upheld the affirmative action program, which allowed universities across the country to use race as a factor for admission.