There are two studies that I am aware of that show non nurses send students home more often than nurses who can assess them and send back to class when appropriate:
Wyman, L. L. (2005). Comparing the number of ill or injured students who are released early from school by school nursing and nonnursing personnel. Journal of School Nursing, 21(6), 350–355. (57% more often than nurses )
Buchwalter, P. (2005). Differences in school health practice between school nurses and unlicensed assistive personnel
http://apha.confex.com/apha/133am/te...per_110412.htm (nurses were significantly more likely than UAP to return students to class)