The actual figure appears to be about 45%, though it takes a little sorting to determine.
According to the enrollment figures for the Arizona Department of Education on their Accountability & Research page for the 2016-17 school year, 511,608 of 1,126,441 public school students were "EthnicHispanicLatino," which is 45.4 percent.
But that includes high school grades 9-12; Arizona grade school is broken down as grades 1-8.
The grade school student number was 44.9%, according to my crunching of the Arizona Superintendent of Public Instruction's Superintendent’s Annual Report for Fiscal Year 2014-2015, the most recent report posted by the Arizona Department of Education at http://www.azed.gov/superintendent/superintendents-annual-report/.)
(Figures are for Fiscal Year 2013-14 and may have changed.)
For students enrolled in grades 1-8 in district schools, 272,638 of 580,000, or 47.0%, were identified as Hispanic.
For students enrolled in grades 1-8 in charter schools, 35,887 of 106,277, or 33.8%, were identified as Hispanic.
Aggregated, that's 308,525 Hispanic students out of 686,917 total students, for 44.9%.
Which does raise the question of how students are determined to be Hispanic, which turns out to be based on what Arizona labels Federal Race/Ethnicity Data Guidance, which appears to be summed up by the federal Department of Education as "New Race and Ethnicity Guidance for the Collection of Federal Education Data," from August 2008.
Generally, "Hispanic" is an ethnicity, typically self-reported, so both Hispanic and non-Hispanic categories include American Indian/Alaska Native, Asian, Black/African American, Native Hawaiian/Other Pacific Islander, White, and Multi-Racial.