PORTLAND — Portland on Tuesday will hold a citywide referendum on the school system’s $94.2 million budget for the 2012-13 school year.

Voters will be asked: “Do you favor approving the Portland School Budget for the upcoming school year that was adopted at the latest City Council budget meeting?”

The City Council last week voted unanimously to approve the budget after the Portland Board of Public Education cut about $600,000.

State law requires school districts to hold elections for final approval by a majority of voters. The budget must be approved by a majority of voters.

The $4.7 million in additional spending over the current school budget would boost expenditures by 5.3 percent, raise an additional $2.7 million from property taxes and increase the tax rate by 3.7 percent.

Education spending accounts for nearly a third of the city’s total expenditures. The combined school and city budgets would increase Portland’s property tax rate by 2.9 percent. The tax rate would increase 54 cents, from $18.28 per $1,000 valuation to $18.82. For a home assessed at $200,000, taxes would go up $108.

The City Council will make a final decision on the city’s $206.4 million budget on May 21.

The school budget includes a $71,000 increase for English language courses run by Portland Adult Education.

Those courses have had a surge in enrollment in recent years, creating a waiting list of 160 people. The additional funding would cut the waiting list by half.

The school board’s big new initiative calls for upgrading the computers used by teachers and students, including replacing Dell Netbooks used by high school students with laptops.

For elementary schools that now have old computers, the school board wants to replace computer labs with a system in which computers are brought into classrooms on carts.

The school board had proposed spending $526,000 as the first payment in a four-year lease-to-purchase plan for new computers and wiring upgrades. The plan would cost $2 million in the fourth year.

The City Council, however, decided that it would be cheaper to borrow than make lease payments and removed that money from the operating budget.

Instead, the City Council plans to borrow the money for computer upgrades, although no final decision has been made.

Once the budget process is finished, the City Council will decide which city and school projects should be funded with borrowed money.