Students will have to demonstrate mastery of English to graduate from Colorado public high schools under a bill approved overwhelmingly in the Senate this morning.

Under SB 73, each of the 178 school districts will decide how to determine mastery. But they will not be allowed to use scores on statewide achievement tests, which are given only through 10th grade.

The districts have five years to adopt the standards.

Sen. Chris Romer, D-Denver, the chief sponsor of the bill, said the bill will spark discussion in school districts about how to equip foreign-born students for the workplace while maintaining a multicultural society.

"The public yearns for a thoughtful discussion about assimilation, not just immigration," Romer said. "You have to send a signal about assimilation. That doesn't mean we can't be multilingual."

The bill passed on a voice vote. A tallied vote is scheduled for Wednesday, after which the measure proceeds to the House.

Opposition came from Sen. Sue Windels, D-Arvada, the chairwoman of the Senate Education Committee.

She said schools will be hit with the cost of additional English programs. If students fail to graduate, districts will incur the extra cost of educating them for an additional year.

The big problem will be students who show up in their junior or senior year with few English skills, Windels said.

Romer said those students will need intensive instruction, which might take time from other subjects, such as math. Romer is on the board of New America Schools, which operates three charter schools exclusively for students who don't speak English.