This 2015 file photo shows a vacant classroom at Southwestern High School in Detroit, where schools have faced a fiscal crisis. Michigan is among the states spending less now on education than before the recession. (AP Photo/Carlos Osorio)

When the Great Recession hit, states trimmed — and in some cases slashed — their budgets for public services, including for education. As the recession ended and the economy improved, some states began restoring funds to schools. But by 2014, 35 states were still spending less per student than they did in 2008, before the recession took hold, according to a report released Thursday.

Data for total state education spending in the current school year isn’t yet available. But looking just at general (or “formula”) funding, which comprises the bulk of education spending in most states, 23 states are continuing to spend less per student in the 2016-2017 school year than they were in 2008, according to the report by the Center on Budget and Policy Priorities, a left-leaning think tank.

In too many states, “public investment in K-12 schools, which are crucial for communities to thrive and the U.S. economy to offer broad opportunity, has declined dramatically in recent years,” said Michael Leachman, a co-author of the report.

Here are the states with the biggest declines in total state spending from 2008 to 2014, on the left, and 2008 to 2017, on the right:

An obvious outlier is North Dakota, where a booming oil industry filled state coffers and made possible an enormous increase in per-pupil spending.

Why are states still spending less than they were in 2008? Some states have been slow to recover from the recession, and they have had to deal with rising enrollments and rising costs at the same time as federal education aid dipped, according to the report. But Leachman pointed out that several states with the largest decreases in school spending — such as Arizona, Kansas, North Carolina, Oklahoma and Wisconsin — also have cut income taxes in recent years, giving up revenue that could be used for education.

State tax dollars account for nearly half of education funding nationwide, so the decline in state funding has left many localities with a difficult choice: Raise local taxes, cut services and lay off teachers, or both. Leachman said that even when localities try to raise revenue, they often aren’t able to make up for lost state dollars.

Here is a chart showing changes in total state and local funding from 2008 to 2014: