PORTLAND — The city is holding a referendum today on the school system’s $94.2 million budget for the 2012-13 school year.

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.