AUGUSTA — The time for lawmakers to scrutinize how Gov. Paul LePage’s biennial budget proposal will affect public schools remains weeks away, but the state’s largest teachers union is already drawing battle lines.

Officials from the Maine Education Association, which has 24,000 members, gathered teachers from across the state on Friday in Augusta to argue that LePage’s laser focus on cutting the state’s income tax will come at the expense of Maine’s public schools.

“We want you to know that we believe the tax changes will devastate our schools, our teachers and the future of our state,” said Maine Education Association President Lois Kilby-Chesley. “When costs go up and state funding stays the same, it costs students in our classrooms. We need to be taking a long-term view.”

LePage’s proposed biennial budget includes initiatives that would force reductions in spending or tax increases at the state, county and local levels if enacted.

One of the major items is a sweeping tax reform proposal that seeks to lower Maine’s income tax rate, as well as a range of smaller tax cuts, while increasing the sales tax rate and base. The sales tax hikes are proposed to go into effect next year, while the income tax wouldn’t be fully implemented until three years from now. That sets up what Kilby-Chesley, teachers and a number of lawmakers call a fiscal cliff of about $300 million in fiscal year 2018.

One LePage proposal, which would take effect on July 1 if his budget is enacted, would require cities and towns to raise more money from property taxes than they currently do to receive their full allocation of state aid to education. Municipalities are required to raise $8.10 for every $1,000 of assessed value to trigger full funding for their school district; LePage proposes increasing that to $8.44 per $1,000.

Determining how much that will affect municipalities involves a range of estimates, but the Maine School Management Association has estimated that the change would cost municipalities tens of millions of dollars annually.

A LePage spokeswoman said the governor has proposed funding increases for education in all three of his biennial budgets. Those increases total $148 million more than former Gov. John Baldacci and the Legislature appropriated in the 2010-11 biennium, though Baldacci’s final figure was heavily influenced by the onset of the Great Recession. In addition, the state’s per-pupil spending has gone steadily upward since 2011, though that also is a function of the loss of about 8,000 public school students since then.

“We’ve been flying on a bare-bones budget for years,” said Steve Knowles, a science teacher at Woodland Junior-Senior High School in Washington County. “When my older son gets to ninth grade, we’ll be using science textbooks from 2001. … I also have a 2-year-old daughter, and I hope that when she gets to ninth grade, we’re not still using those same 2001-year textbooks.”