Hello,

Your question is ambiguous. School doesn't provide online classes. there are online coaching for entrance exam (AISSEE) which is accepted by Sainik school. there are some private webpages which provides materials. Some online webpages for paid online course to crack exam. Youtubers who provide free learning and paid too.

most important out of all is how much effort you can put into it. how much time you can invest to learn, understand and solve problems. That is the only thing which is needed which will make you to perform well.

Hope it helps!