Can students ask permission to access blocked websites

Yes, as an admin you can allow students to ask for permission to access the blocked websites when they come across a blocked page. To do this, you would need to enable the Contact Admin button in Policy Editor > Global Settings. This will only apply when the student is on site (within your IP range) and will not apply to Parent or Take Home policies. 

The student would then be displayed a button asking them to request permission. The student is required to enter an email address and reason for wanting to access the website.

The admin can allow the website by adding it to the Global Allow list.