Ashley Hughes, 19, who had only been at the University of Lincoln a few months, died of an overdose after taking two ecstasy tablets in December last year.
Reis Bilal, Luke Green, both 19 and Haydon Watson, 21, admitted drugs supply charges following his death.
They were given jail terms of between one and three years.
Lincoln Crown Court heard the teenager, from Gateley, Cheshire, had collapsed after taking drugs and was pronounced dead a short time later.
His friend Luke Green admitted buying them for him from fellow student Reis Bilal after they pooled their cash to get eight tablets.
It was later discovered Bilal obtained the drugs from third year student Haydon Watson.
Following the sentencing, Ashley's mother Lisa Leigh said: "I find it very hard to accept what has happened just because of Ashley's nature.
"In my heart I knew he didn't drink, smoke, and certainly was not interested in drugs. What people don't see is the pain and hurt for the family and friends left behind.
"If it was a car accident I could accept it, but not this. It was so out of character. He was at university for 13 weeks but people don't change in that short time.
"I have read text messages on his phone in his own words saying that it was peer pressure."
She added: "There should be no mercy for people who sell drugs and prey on the innocent minded.
"I feel sorry for the boys' families at what monsters they have become. I would gladly swap places with them as at least they can still see and speak to their boys."
Bilal, 19, of Ruston Way, Lincoln, was sentenced to two years in a young offenders' institution; Green, 19, of Grantham Street, Lincoln, was handed a 12 month sentence.
Watson, 21, of High Street, Lincoln, was jailed for three years.
A mother has blamed "peer pressure" for the death of her son as three fellow students are jailed for supplying the drugs that killed him.