Problem on add permission on folder with CACLS

Hi everyone,

I'm using a command shell to run the cacls command to add permissions on students personal folders right after the student's active direcory account has been created. It was fine when I test the code with single account. But when large amount of students are involved some students can't access to their folders. When I look at those students' folders, the permissions are set perfectly. If I remove the permissions and reset the exact same permissions they are albe to access their folders. I have no clue how this happens. Is anyone familiar with this problem? And is there any alternative way to achieve what I'm doing now. I really appreciate for your help and suggestion.
Thanks!