MOUNTAIN VIEW (CBS) — A Mountain View High School history teacher who stirred controversy earlier this month after asking his students to compare president-elect Donald Trump to Hitler has decided to retire.

But while Frank Navarro is at retirement age, that’s not why he is ending his career after 40 years of teaching.

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“I’ve decided to retire now because I’m really disappointed in the way I was treated,” said Navarro.

The Mountain View-Los Altos School District put him on paid leave after the election. Navarro said it happened when a parent complained about his controversial lesson plan.

“I was dismissed that day, explained Navarro. The lack of respect, understanding and the unwillingness to even talk about that ideas…”

His students started an online petition to get him back in the classroom. The following week, the district brought him back without saying why.

But the superintendent did issue a letter to parents saying, “the teacher’s paid leave was not for teaching a lesson comparing Trump to Hitler.”

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That statement is contrary to what Navarro told KPIX 5.

“I’m curious, because the meeting we had was all about that comparison,” said the teacher.

Navarro, who studied at the International Center for the Study of the Holocaust, said he’s sticking by his lesson.

“History doesn’t repeat itself, but like Mark Twain says, it sure rhymes. And that’s what I was looking at,” said Navarro.

When he leaves Mountain View High at the end of the school year, Navarro said he won’t miss school politics. But he will miss his students.

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“My students make me want to be a better teacher,” said Navarro. “I often look at that at the end of the day: ‘Who am I? What am I about?’ So it’s time to go.”