In a statement headteacher Julia Vincent said: “We are very sorry and saddened to hear the news about Ryan Lock.
“He was a well-liked pupil during his time at Warblington School. Our thoughts go out to his friends and family at this time.”
Mr Lock, 20, said to be a chef from Chichester, was a pupil at Warblington School for four years after joining in October 2008 from Portsmouth.
Social media has also seen tributes paid to Mr Lock with posts on Twitter referring to him as a volunteer.
He was said to have no military experience and was reported dead by Kurdish activists, according to the BBC.
In the report it states Mr Lock travelled to join Kurdish forces known as the YPG against so-called Islamic State in August and was killed on December 21 in the battle for the Syrian city of Raqqa.
Don’t miss out on all the latest breaking news where you live.
Here are four ways you can be sure you’ll be amongst the first to know what’s going on.
1) Make our website your homepage
2) Like our Facebook page
3) Follow us on Twitter
4) Register with us by clicking on ‘sign in’ (top right corner). You can then receive our daily newsletter AND add your point of view to stories that you read here.
And do share with your family and friends - so they don’t miss out!
Always the first with your local news.
Be part of it.