11. Six candidates are sitting in the same row of seats with a passage on each side to take an exam. The order in which the candidates finish their papers is uncertain, and each person leaves their seat and exits the classroom immediately after finishing. Then the probability that at least one person will disturb other students still taking the exam when they hand in their paper is $\qquad$ .
11. $\frac{43}{45}$.

To avoid disturbing other students who are still taking the exam, one must leave only after the two students sitting next to them have left, meaning there are two choices each time, resulting in a total of $2^{5}$ possibilities. Therefore, the required probability is $1-\frac{2^{5}}{6!}=\frac{43}{45}$.