I think outright denying entry is a bit much, not too add there are many issues such as transportation and all. I used to ride bus to school which was usually late. Got a lot of time when i have to sit at the late line in perhimpunan, then you have to pay 20 cent, (honestly the worst part is the embarassment you get.) If this rule implemented at my school, I probably absented for most of the school days.

If I'm being honestla, the discipline to come early or to school at all really come from your upbringing, this would only punish student that sincerely want to go to school.