Andrew Moffat, the assistant headteacher of Parkfield Community School in Birmingham, said he felt "vulnerable" after being sent a number of unkind messages.
He said: "When you read them, it makes you feel vulnerable. But you have choices.
"What choice do you have? You either let it stop you or you carry on and it makes you stronger."
Parkfield Community suspended Mr Moffat's No Outsiders programme at the end of last month while it sought to strike a resolution with parents.
The majority of children at the school are from Muslim families.
Some parents, including Christians, were angry about the programme's teaching on lesbian, gay, bisexual and transgender lifestyles.
Defending it, Mr Moffat said: "Let's not forget that some of our children have two mummies or daddies. What we can't say to them is, 'don't talk about your family."
New guidance published by the Government makes relationships education compulsory in primary schools, while sex and relationships lessons have become compulsory in secondary schools.
Mr Moffat's teaching plan incorporated a number of books - including one which told the story of a boy who wore a dress.
He said: "The central message is; whatever your religion and whatever your beliefs, we can co-exist. I'm not undermining any religion or faith.
"I'm just saying, 'yes, there are different beliefs in the UK, that's what makes the UK a great place to be. We can have different religions."
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