5. Arizona
> Overall grade: D+
> State Score: 67.6
> Per pupil spending: $8,101 (2nd lowest)
> High school graduation rate: 77.0% (12th lowest)
> Eighth graders proficient in math or reading: 30.6% (14th lowest)

School districts in Arizona spent $8,101 per pupil in 2012, the second lowest average expenditure nationwide. As in most of the worst-rated states, Arizona allocates relatively little tax revenue to education. The state spent just 2.5% of state GDP on education in 2012, nearly the lowest proportion of any state. On average, across the U.S. education expenditure accounted for 3.4% of state GDP. As in other states with high proportions of immigrants, many children from Arizona’s non-english speaking families may find instruction more difficult than their peers. Less than 78% of children had parents who were fluent English speakers, one of the lowest rates in the country. While more than 34% of eighth graders nationwide were proficient on reading exams, less than 28% in Arizona were, one of the lowest rates.

ALSO READ: America’s Worst Run Companies

4. Oklahoma
> Overall grade: D+
> State Score: 67.6
> Per pupil spending: $8,624 (7th lowest)
> High school graduation rate: 79.0% (21st lowest)
> Eighth graders proficient in math or reading: 25.0% (6th lowest)

More than 34% of eighth graders nationwide demonstrated proficiency on the NAEP in 2013. In Oklahoma, just 25% of eighth graders did so, one of the lowest rates reviewed. While high education expenditures do not guarantee better performance on national exams, relatively small school budgets in Oklahoma likely played a role in the students’ poor performance. School districts spent $8,624 per pupil in 2012, among the lowest average expenditures. Similarly, children from wealthier backgrounds can often count on more advantages than their less wealthy peers, and Oklahoma residents were relatively poor in 2013. Less than 45% of adults earned incomes at or above the national median, one of the lower proportions in the country.

3. New Mexico
> Overall grade: D
> State Score: 65.5
> Per pupil spending: $9,736 (16th lowest)
> High school graduation rate: 74.0% (6th lowest)
> Eighth graders proficient in math or reading: 22.7% (4th lowest)

The four-year high school graduation rate in New Mexico was less than 74% in 2012, below the national graduation rate of 81%. New Mexico’s students also performed poorly on standardized assessment tests, with just 21.5% of fourth graders deemed proficient in either math or reading. Nationally, 34% of fourth graders were proficient in either subject. Poor test scores may be a reflection of insufficient funding. New Mexico’s school districts spent an average of $9,736 per student in 2012, roughly $2,000 less than average spending level across the nation.

ALSO READ: States Where People Live Longest

2. Nevada
> Overall grade: D
> State Score: 65.0
> Per pupil spending: $8,141 (5th lowest)
> High school graduation rate: 60.0% (the lowest)
> Eighth graders proficient in math or reading: 28.3% (10th lowest)

Less than 34% of children in Nevada had at least one parent with a post-secondary degree, the lowest rate nationwide. Since parents play perhaps the most important role in a child’s chance for success, poor educational attainment rates among adults in Nevada were likely a factor in children’s relatively poor achievements in school. Similarly, early education can set the stage for a child’s entire academic career. Young children in Nevada were among the least likely nationwide to attend preschool or kindergarten. With the lowest high school graduation rate in the country, at 60% in 2012, young adults in Nevada were also far less likely to pursue further education than their peers in most states. While 55.1% of American young adults were enrolled in or had completed a post-secondary degree program, just 40.5% in Nevada were — nearly the lowest rate.

1. Mississippi
> Overall grade: D
> State Score: 64.2
> Per pupil spending: $9,587 (15th lowest)
> High school graduation rate: 68.0% (2nd lowest)
> Eighth graders proficient in math or reading: 21.3% (3rd lowest)

Mississippi had the worst schools in the country in 2013, receiving a D on Education Week’s report. The state’s K-12 achievement was particularly poor — Mississippi was only state to earn a failing grade in the category. Less than 22% of fourth and eighth grade students were deemed proficient in either math or reading, far below the 34% of students considered proficient nationwide in each age group. Poor test scores may be a product of the state’s poverty. Roughly 58% of families earned incomes that were less than 200% of the poverty level in 2013, higher than the nearly 45% of families who did nationwide. Additionally, only 38.4% of children had at least one parent who had a post-secondary degree in 2013, one of the lower rates nationwide. Finances, too, were a major problem for school districts in Mississippi. On average, districts spent less than $10,000 per student in 2012. Although it wasn’t the lowest per pupil spending, it was just half as much as Vermont, the nation’s highest per-pupil spender.

Click here to see America’s best school systems