MADISON, Wis. (AP) -- Gov. Scott Walker has signed a bill that limits expansion of Wisconsin's school voucher program.

The voucher program subsidizes private education for students in struggling school districts. The program had been limited to the city of Milwaukee, but Republicans included new qualifiers in the state budget that extended the program throughout Milwaukee County and the city of Racine.

Opponents complained the new criteria was so broad students across the state could qualify. Rep. Robin Vos, a Republican who co-chairs the Legislature's budget committee, said that was never the intent and GOP lawmakers passed a bill that limits voucher participation to school districts in the program when the bill took effect. Any additional districts would need separate legislation to join.

Walker signed the bill Thursday but announced the signing Friday.