(CNN) Johan van Hulst, a former Dutch senator and teacher renowned for his efforts to save hundreds of Jewish children during the Holocaust, died March 22 at the age of 107, the Dutch Senate announced this week.

As principal of the Reformed Teachers Training College, van Hulst found himself at the center of a growing operation to smuggle Jewish children out of Amsterdam to protect them from Nazi persecution during the Second World War.

The college garden bordered that of a Jewish day-care center, from which hundreds of Jewish children were passed over the garden fence to be temporarily hidden by van Hulst before being collected by members of a children's rescue organization and smuggled to safety.

"Try to imagine 80, 90, perhaps 70 or 100 children standing there, and you have to decide which children to take with you.... That was the most difficult day of my life," he remembered of the period in 1943 when the Jewish day-care center was due to be cleared out, according to Yad Vashem , the World Holocaust Remembrance Center.

"You realize that you cannot possibly take all the children with you. You know for a fact that the children you leave behind are going to die. I took twelve with me. Later on I asked myself: 'Why not thirteen?'"

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