Admission time is the crazy time for all websites. School websites will get an unexpected number of hits on the day their admission application form goes online.
So what and how to handle the issues like these:

1. Unable to open the school website
2. Unable to submit form

First of all, do not open the website in the peak period.
Peak period is 8am to 2pm and 4pm to 9pm.
So you get a cool period of 2 hours between 2pm to 4pm and after 9pm to fill the form.

Another trick is to open at least 3-5 form on 1-2 devices of the same form.
Fill one and submit.
If it is accepted, close all other forms.
Else you have nothing to worry. Start filling in all other forms one by one.

Trust me, it will work.

And last but not the least, get all information ready and fill the form v quickly.
Sometimes, the forms have time limit and session ends if you open it for too long.

So get to filling the school forms.