University Admission Handbook published by University Grants Commission contains Z-score table.
This table gives Minimum Z score cut off values for selection of various University courses in each district. 2016-2017 University handbook contains Z score values for 2015 GCE A/L Examination.
Download Z Score Table2015 A Level Z score cut off marks
If you need to check whether you are eligible to enter into Universities based on A/L examination read these posts also.
Z Scores Cut off marks for University admissions 2016 based on 2015 A/L results
District and Merit quotas: How to check your University, Faculty based on Island Rank IR and District Rank DR?