The sentence doesn't read very natural to me. I'll critique it to give you some ideas.
- "... DIDN'T FEEL sad despite PARTING ..., because they RETURNED ..." is unnatural.
Make it DIDN'T FEEL ... because they WERE RETURNING ..., to mean how they were feeling about going home.
- "despite" seems to be unnecessary. I think it sounds better without it.
- "parting with" a place doesn't sound natural. You part with a thing or person, not a place.
- "this place" might not be a good choice as it can sometimes sound derogatory. Better to be more specific.
- "fully loaded" doesn't sound like a good choice in this context.
I would write something like these:
- They didn't feel sad to leave the school, because they were returning home more knowledgeable and accomplished.
- They had no regrets heading home, as it had been a time well spent with a lot gained.
- They felt good when it came time to go home, because they believed they had completed a productive N years of their lives. (substitute actual number for N)