The analysis of heart rate variability (HRV) is one tool shown to be of value in examining heart-brain interactions. HRV is remarkably responsive to emotion, and the importance of emotional state in cognitive function is increasingly being recognized and socio-emotional learning strategies being utilized in the classroom. Consequently, the application of HRV data may be useful in increasing positive emotional behavior and academic performance and helping to establish optimal learning environments. The setting: 22 elementary schools in California--14 Adventist schools (n = 204) and 8 public schools (n = 205). HRV/pulse wave data was recorded using a Biopac MP35 data acquisition system. One-way ANOVA, performed to assess the difference between HRV measures (SDNN, RMSSD, HF, LF, VLF, TP, LF/HF, and COH) across ages (5 to 14) and gender, and between Adventist and public schools, revealed the following: (a) A significant difference in HRV measures according to age, contributing to HRV formative data for elementary-age children across this decade. No significant difference in HRV was found with regard to gender (189 male, 220 female). (b) A significant positive difference in he HRV-Coherence measure between students in Adventist schools and in public schools; Tactical significance, however, was small. Multiple regression, performed to assess the relationship of HRV to behavior (SESBI-R) and achievement scores (ITBS & CST) produced these findings: (c) The relationship between HRV measures and problem behaviors according to SESBI-R was inconclusive, while (d) the relationship between HRV and ITBS achievement test scores was conclusive in reading, language arts, and composite scores, although the correlations were near zero and therefore had little practical value; CST achievement score results were inconclusive. The data did not show a strong practical relationship existing directly between HRV measures and academic achievement test scores in elementary school children. Additional studies are needed to confirm findings relative to HRV and academic performance. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]