The history-making approval of budgets in all of Long Island’s 124 public school districts this week can be credited in large part to state policies aimed at keeping taxes in check — particularly the property-tax cap, experts said Wednesday.

Voters’ adoption of spending plans in all the systems was the first time the region produced a 100 percent passage rate since one-day balloting began in 1996. Budgets are for the 2017-18 school year.

Nor was the Island’s voting an isolated example of taxpayer support.

Record-setting statewide passage rates of 99 percent-plus were reported Wednesday by two Albany-based advocacy groups.

One was the New York State School Boards Association, representing more than 5,000 trustees throughout the state. The other organization was the Empire Center for Public Policy, a conservative think tank.

The nonprofit groups, which often disagree on school finance issues, concurred Wednesday on a central point: The state’s five-year-old tax-cap law, by restricting annual growth in property taxes, has helped build public support for school budgets that account for roughly 65 percent of homeowners’ bills.

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“The tax-cap effect was on full display in yesterday’s school district budget voting,” said Kenneth Girardin, communications and marketing manager at the Empire Center.

Girardin estimated that budgets passed in 99.3 percent of 669 districts statewide. He noted, in particular, Newsday’s report of universal passage on the Island.

The school board association’s figure was slightly higher: 99.4 percent passage in 671 districts statewide. But the primary conclusion was similar.

“I think the cap has helped keep tax increases low and that, in turn, has led to some of the high passing rates we’ve seen,” said David Albert, an association spokesman.

The cap law limits yearly increases in property taxes to 2 percent or the inflation rate, whichever is lower. This year’s statewide baseline cap is 1.26 percent.

Local district caps can run higher or lower, depending upon their own financial circumstances. The law is one of the nation’s tightest, and has captured a great deal of public attention since Andrew M. Cuomo pushed for it during his first gubernatorial campaign in 2010.

“The voters have spoken and they clearly appreciate the fiscal restraint and savings attributable to the property tax cap, especially as the state increased education aid to a record $25.8 billion,” Cuomo spokesman James Allen said Wednesday.

School officials and others noted that the caps are part of a broader system that provides alternate sources of school funding, along with incentives for cap compliance and penalties for noncompliance.

Another Cuomo initiative, for example, links state financial aid for school districts to growth in personal income. The idea is to provide schools with a predictable source of state money, derived mostly from income taxes, as compensation for restrictions on revenue from local property taxes.

Next year, state assistance to schools on the Island will increase 4.1 percent, well beyond inflation.

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John Lorentz, superintendent of Farmingdale schools, spoke for many of his colleagues recently in welcoming the extra help.

“We’re much more dependent on state aid, so it’s that much more valuable,” Lorentz said.

The cap legislation, along with annual expansions in school aid, have enjoyed bipartisan support in the Legislature. Senate Majority Leader John J. Flanagan (R-East Northport) pointed to the contribution made by his fellow Republicans toward the latest school budget adoptions.

“Together we have shown that it is possible to reduce New York’s tax burden and continue making smart investments that will support our schools,” Flanagan said in a prepared statement.