A recent brush with a "life-threatening medical illness," which he did not name, caused him to re-evaluate his priorities and seek greater work-life balance, the 36-year-old principal said.
Marilyn Cook, a former principal of Paly, has agreed to step in as acting principal pending the hiring of Winston's replacement. The search already has begun, Superintendent Kevin Skelly said Tuesday.
"We appreciate (Winston's) deep dedication and strong service to our community in this role," Skelly said.
In an email to the Paly community sent late Monday night, Winston said the illness had caused him to reconsider his personal and professional goals.
"At this stage in my life, spending time with my family, protecting my physical health and having a better work-life balance are my top priorities," he wrote.
Winston said he has asked to be reassigned as a teacher.
Skelly said Winston has "done a great job with kids and parents (at Paly).
"He's just worked really hard on the environment at the school. His smiling face on the campus, his approach to the work has been really positive."
Winston is known for his visibility around the high school campus. He recently proposed to move the principal's office to the school library as part of a school remodeling project so as to be physically closer to the center of student activity.
The former special-education teacher and assistant principal at Gunn High School was named to the Paly job in 2010, at 33.
Winston taught special education for six years in Milpitas, where he grew up and now lives with his wife and two children, before joining the Palo Alto district as a special ed teacher at JLS Middle School.
"A piece of my heart" will always be in special ed, he once said.
Winston attended Mission College and earned a degree in psychology from California State University at Hayward (now Cal State East Bay). He earned a teaching credential at Santa Clara University.
A hallmark quote, which adorned his office wall at Gunn and Paly — and which he read aloud three weeks ago at Paly's May 29 graduation ceremony — is from 18th Century English Parliamentarian and abolitionist Thomas Foxwell Buxton: "With ordinary talent and extraordinary perseverance, all things are attainable."
When he was hired as the Paly principal, Winston said his goal was to "understand the community (and) keep it student-centered."
"Student-centered" means "continuing to process decisions and how the school functions based on what is best for our students in all areas — academics, student life, culture, social, emotional, guidance, support and extracurricular activities," he said at the time.