There are 38 students in total. The probability, p, of choosing an elementary student=25/38, and the probability of not choosing an elementary student, 1-p, is 13/38. This is a binomial situation expressed by (p+(1-p))^5 (=1, certainty) which expands to: p^5+5p^4(1-p)+10p^3(1-p)^2+10p^2(1-p)^3+5p(1-p)^4+(1-p)^5. Each term has a meaning: p^5 is the probability of selecting 5 elementary students; 5p^4(1-p) the probability of exactly 4 elementary and one high school student; etc. The probability of at least 2 elementary students is the sum of the probabilities of exactly 2, 3, 4 or 5 elementary students; or it is 1 minus (sum of the probabilities of all high school and exactly one elementary school student)=1-(1-p)^5-5p(1-p)^4=1-(13/38)^5-5*25/38(13/38)^4=0.95026 or 95.03% approx.