1. | (11) | Journal article | Qualitative study and was based on a questionnaire-based survey | 32 school principals | Higher secondary education | Malaysia |
2. | (12) | Journal article | Qualitative study and was based on a questionnaire-based survey | 316 school principals | Secondary and primary education | Sweden |
3. | (13) | Journal article | Qualitative study and was based on a questionnaire-based survey | 57 school principals | Secondary and primary education | Philippines |
4. | (14) | Journal article | Qualitative study and was using a multiple-case design based on rigorous interviews | Not mentioned | Secondary, primary, and higher education | United States and India |
5. | (15) | Journal article | Small-scale qualitative study and was based on interviews | 12 school principals | Secondary and primary education | United Kingdom |
6. | (16) | Journal article | Implementation of qualitative study and was based on SWOT analysis and interviews | 7 school leaders | Only primary education | Jamaica |
7. | (17) | Dissertation | Exploratory qualitative case study and was based on interviews | 12 school principals | Only secondary education | United States |
8. | (18) | Dissertation | Qualitative study and was based on electronic survey questionnaire and structured interviews | 15 (questionnaire) 10 school principals (interview) | Secondary and primary education | United States |
9. | (19) | Dissertation | Qualitative phenomenological study and was based on interviews | 11 International School Heads (ISH) | English-medium NGO international schools | around the globe |
10. | (20) | Journal article | Qualitative research projects and was based on interviews | 66 school principals | Only primary education | United Kingdom |
11. | (21) | Journal article | Qualitative case study and was based on interviews | 30 K-12 leaders | primary education | United States |
12. | (22) | Journal article | Phenomenological qualitative study and was based on interviews | 12 school principals | primary education | Philippines |
13. | (23) | Journal article | Qualitative study based on a survey questionnaire | 93 teachers and 5 school principals | Secondary and primary education | North Cyprus |
14. | (24) | Journal article | Qualitative case study and was based on interviews | 11 school principals | primary education | Canada |
15. | (25) | Dissertation | Qualitative study and was based on semi-structured interviews | 11 school principals | primary education | United States |
16. | (26) | Journal article | Qualitative case study and was based on semi-structured interviews | 8 superintendents | public mainstream education | United States |
17. | (27) | Dissertation | Phenomenological qualitative study and was based on interviews | 14 high school principals | Only secondary education | United States |
18. | (28) | Journal article | Quantitative study and was based on a survey questionnaire | 27 school principals | Only secondary education | Philippines |
19. | (29) | Journal article | Phenomenological qualitative study and was based on interviews | 93 school principals | Secondary and primary education | Turkey |
20. | (30) | Journal article | Qualitative study and was based on project management reports and interviews | 6 school principals | Only secondary education | Italy |
21. | (31) | Journal article | Phenomenological qualitative study and was based on semi-structured interviews | 17 teachers and 2 school principals | Only primary education | Indonesia |
22. | (32) | Journal article | Qualitative study and was based on interviews | 10 school principals | Secondary and primary education | United States |
23. | (33) | Journal article | Qualitative study and was based on interviews | 11 school principals and 2 faculty heads | Secondary and primary education | around the globe |
24. | (34) | Journal article | Qualitative case study and was based on semi-structured interviews | 15 school principals | Secondary and primary education | Turkey |
25. | (35) | Journal article | Qualitative case study and was based on semi-structured interviews | 2 school principals and 8 teachers | Only special education | Japan |
26. | (36) | Journal article | Qualitative study and was based on interviews | 15 school principals | Only primary education | Norway |
27. | (37) | Journal article | Qualitative study and was based on semi-structured interviews and survey questionnaires | 10 school principals | Only secondary education | S. Africa |
28. | (8) | Journal article | Qualitative study and was based on semi-structured interviews | 55 school principals from 43 school organisations around the world | Only secondary education | International Schools, United States and China |
29. | (38) | Dissertation | Qualitative study and was based on semi-structured interviews | 9 school principals | Secondary and primary education | around the globe |
30. | (39) | Journal article | Qualitative study and was based on semi-structured interviews | 8 school principals | Secondary and primary education | India |
31. | (40) | Journal article | Qualitative study and was based semi-structured interviews and note-taking | Not mentioned | Secondary and primary education | Philippines |
32. | (41) | Journal article | Pilot qualitative study and was based semi-structured interviews | 17 school principals | Only secondary education | Canada |
33. | (42) | Journal article | Quantitative study and was based on a survey questionnaire | 204 school principals | Only primary education | Spain |
34. | (43) | Dissertation | Quantitative study and was based on autobiographical data from case studies | 4 school principals | primary and secondary education | United States |
35. | (44) | Dissertation | The qualitative multi-case study was based on a survey questionnaire and interviews | 6 school principals | Private primary education | United States |
36. | (45) | Journal article | Qualitative study was based on structured interviews | 9 school principals | secondary and primary education | United States |
37. | (46) | Journal article | Qualitative study and was based on interviews | 5000 school principals working in special education | Only special education | Canada |
38. | (47) | Journal article | A qualitative study and was based on a questionnaire with open-ended questions | 57 school principals | primary and secondary education | Greece |
39. | (48) | Journal article | Qualitative study and was based on interviews | 18 school principals | secondary education | New-Zealand |
40. | (49) | Journal article | Quantitative study and was based on a survey questionnaire | 30 school principals | K-12 education | United States |
41. | (50) | Journal article | Mixed methods study and was based on a survey questionnaire with closed and open-ended questions | 251 school principals, heads, and managers | primary and secondary education | Austria |
42. | (51) | Journal article | Case study | 1 school principal | secondary education | United States” |