Dear @Sheetal,
Children have a very tender psychology. I profess that parental touch is a must for every child. You must have had a strong reason to send your 7 year son to hostel, but child emotions search for Parental love & support. You said they miss home, likewise, I am sure you also miss them ….don’t you??
Please request VK and give both of them "Bravo Serum". Only their confidence, while living without parents, will usher them towards studies. Try more to be in touch with them and give support. Also, try to find out about their friends and company, environment in the hostel, as sometimes children are harassed but they cannot complain. Ensure your love to them. I hope everything will be alright.