Bailey Gwynne died after being stabbed in the heart at Cults Academy in October.
His 16-year-old killer, who cannot be named for legal reasons, denied murder and was found guilty of culpable homicide on Monday.
Kate Gwynne said: "Nothing will give us back what has been taken."
She said: "Bailey is not a story. Bailey is our child. He is our son, and our heart, our brother, our grandson, our nephew, cousin and our friend and beloved master of Teddy the Pug."
The statement - accompanied by two new pictures of Bailey - said: "Whatever the outcome was to be in this trial nothing will give us back what has been taken and the only thing that we truly want.
"That is something that we as a family must try to live with.
"Our priority through the time of this trial was to be there for Bailey. That remains our priority along with guiding our sons, his brothers, through this. That is inevitably a long road, but we will never lose sight of Bailey while walking it.
"We have appreciated greatly the support of all those around us and those close to us, whether it has been practical or emotional.
"We know that everyone around us has done their utmost for Bailey and we appreciate and greatly admire the fairness and integrity shown to all parties by the prosecuting counsel.
"We cannot praise highly enough the police, our lovely family liaison officers and the fiscal staff."
It continued: "Our sweet boy with a big dream working hard to make it happen. A boy who was never happier than when chilling out with his friends and his dog after a session in the gym.
"The boy who would carry his brothers to the top on a hill walk when their own legs failed them, who dutifully cut the grass for his dad or rescued his Nonna's shopping and the boy who would come with me on an evening run just to keep me company in the dark even though he could finish it in half the time.
"We will always be immensely proud that Bailey is our son. We now need time and space to come to terms with what has happened and to continue to care for our family and those dear to Bailey.
"Lastly, it has always been a true blessing and a privilege to have Bailey and to share the honour of knowing, raising and loving him. That is not something that time or our parting will ever change.
"Bailey-Bazza, my true gent. With love we hold you in our hearts. Walk tall Bailey-Boy."
The jury at the High Court in Aberdeen took an hour and 40 minutes to find his killer guilty of the lesser charge.
Sentence was deferred until 1 April.
Judge Lady Stacey told the accused he would be sentenced at the High Court in Edinburgh and would be given a custodial sentence.
The youth was also found guilty of two further charges of having a knife and knuckleduster in school.
Following the verdict, it was announced that an independent investigation is to be held into the circumstances that led to Bailey's death.
The mother of a 16-year-old boy stabbed to death in an Aberdeen school has said the outcome of his killer's trial does not bring her "beloved" son back.