The open prison, in Warrington, houses 304 young adults aged 18 to 25.
A report by HM Inspectorate of Prisons found it is "safe", with low absconding rates, low incidence of self-harm and any anti-social behaviour addressed.
However, some prisoners criticised officers as "petty" and complained the food was poor.
The report found security levels were appropriate, but some rules were being used unnecessarily, with disciplinary procedures invoked too hastily.
Most prisoners were engaged in learning and many of those go on to earn qualifications.
Inspector Nick Hardwick said more work was needed to promote diversity and integrate foreign national prisoners.
He added: "In three of our four healthy prison assessments, we have awarded our highest marking, and managers and staff should be commended for this.
"This report highlights a small number of important issues requiring improvement and our recommendations will, hopefully, assist in that process."
Michael Spurr, CEO of the National Offender Management Service, said: "I'm pleased that Thorn Cross has been recognised for its continued good work around preparing the young men for their release."

The result moved Stranraer off the bottom of the division while Airdrie's visit to Brechin City was called off because of a waterlogged pitch.
Queen's Park moved into the top four with a 2-0 win over Stenhousemuir, who slipped to bottom on goal difference.
And Peterhead drew 1-1 with Albion Rovers in the other League One game.
Alloa Athletic v East Fife had previously been postponed due to the Fifers' Scottish Cup meeting with St Mirren. East Fife lost 3-2.
At Ochilview, on-loan Hearts forward Dario Zanatta fired Queen's Park ahead and although the Spiders had Ross Millen sent off for two bookings, Anton Brady added a stoppage-time second for Gus MacPherson's side. They are two points in front of Brechin, who have a game in hand, and a point off Alloa.
Eighth-placed Peterhead led Albion Rovers through Rory McAllister's cool first-half finish but Ross Stewart swept in an equaliser in the second half.
The two sides are level on points - four ahead of Stranraer and Stenhousemuir.
Livi, who threatened through Scott Pittman at home to Stranraer, are 11 points clear of Airdrie and 12 ahead of Alloa.

United boss Louis van Gaal is trying to strengthen his squad after they finished fourth in the Premier League.
Germany international Schweinsteiger, 30, and 29-year-old Spain player Ramos are among those who interest him.
Ramos' contract with Real expires in 2017, while Schweinsteiger's Bayern deal runs until 2016.
Scorer of Real's injury-time equaliser in their Champions League final victory over Atletico Madrid in 2014, Ramos has made 445 appearances for the club since joining from Sevilla in 2005.
He has 128 Spain caps and was in the starting line-up as they won Euro 2008, Euro 2012 and the 2010 World Cup.
Schweinsteiger also has a World Cup winners' medal - starting for Germany in their victory over Argentina last year.
He has been with Bayern all his career and won his eighth league title in May. He also won the Champions League in 2013.
Real's interest in goalkeeper David De Gea will be used by United in their attempt to sign Ramos.
Van Gaal said at the end of last season it would not be easy to keep De Gea - United's player of the year for the second successive year.
The 24-year-old Spain international has refused to extend his contract beyond 2016.
The Red Devils have been linked with several potential replacements during what Van Gaal said could be a "rough" summer for some of his players given the changes he anticipated.
"A club like Manchester United has to be like that," said Van Gaal in May. "When you purchase other players you get a stimulus."
Van Gaal is particularly keen to recruit a right-back, central defender, central midfielder and striker.
United, who have already bought PSV Eindhoven winger Memphis Depay for £31m, are also interested in Tottenham forward Harry Kane.
Barcelona full-back Dani Alves also interested them, but he has signed a new deal at the Nou Camp.
Thorn Cross is "one of the better" prisons, with low levels of violence and high numbers of inmates achieving qualifications, inspectors said.
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Scottish League One leaders Livingston were held to a 0-0 draw with Stranraer while nearest challengers Airdrieonians saw their game postponed.
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Manchester United are interested in signing Bayern Munich midfielder Bastian Schweinsteiger and Real Madrid defender Sergio Ramos.