Neil Bantleman, of Burlington, Ont., and Ferdinant Tjiong, who were arrested in July, say they are innocent, as do a number of fellow teachers and the principal at the Jakarta International School.
They are being tried on charges of violating the Child Protection Law, which provides a maximum penalty of 15 years in jail.
Prosecutors told reporters after a hearing Thursday that the heavy sentences are being sought because as teachers they had traumatized the victims.
"As teachers they have to set a good example, instead of committing deeds that cause trauma to the students that takes a long time to treat," prosecutor Ade Rohimah said.
Defence pleas are scheduled for next week and a verdict is expected April 2.
Guy Bantleman, the brother of the Canadian teacher on trial, says his family is obviously concerned, given the latest news.
"To get to this point with no credible evidence being presented either materially or medically is quite concerning," he said.
"The prosecutors announcing to the media what they're seeking as far as a jail term goes against the judge's directive of not discussing this outside of the court," he added.
In December, five janitors at the school were sentenced to up to eight years in jail in the same case.
They were arrested last April following reports from the parents of a six-year-old boy who said he had been sodomized. Police said a sixth suspect in that group committed suicide while in custody by drinking bathroom cleanser.
The school is attended by children of foreign diplomats, expatriates and Indonesia's elite. It has 2,400 students aged three to 18 from about 60 countries.
Bantleman's family has been urging Ottawa to publicly declare its support for the Ontario man.