Channings Wood prison is performing better than it did before the pandemic, according to the latest official ratings.
The Prison Reform Trust said the latest reports on prison performance show the system is experiencing a "perfect storm" of rising prison population and poor working conditions.
Figures from the Ministry of Justice's prison performance report give ratings based on four main priority areas, security, training, drug and alcohol addictions, and readjustment to society.
The report shows Channings Wood prison received a score of 62% for the year to March 2023, meaning it had a "good performance" rating.
It was an improvement from 61% in 2019-20, the last year ratings were handed out.
Across England and Wales, only 13 of the 119 prisons evaluated were awarded the "outstanding performance" rating, a significant drop compared with the performance in 2019-20, where 19 prisons had achieved the top-tier recognition.
It also showed there was a slight increase in the number of prisons rated as a "serious concern" compared with the previous year. Nine prisons fell into this category, a rise of two from in the previous evaluation.
A Prison Service spokesperson said: "The latest figures show that over half of all prisons are performing well and, where there are issues, we are providing intensive support for those jails to drive long-term improvements, recruit extra staff, bolster security and boost training and work opportunities for prisoners so we can better protect the public."
They added they are working on the "biggest prison expansion" in over a century by building 20,000 new prison places.
Separate data from the Home Office found the rate of prisoners living in overcrowded conditions increased from 21% in 2021-22, to 23% in the most recent year to March.
However, just 9% of the estimated 680 prisoners in Channings Wood were in crowded accommodation.
Pia Sinha, chief executive of the Prison Reform Trust, said the latest figures show the prison system is "chronically overburdened".
She added: "Prisons are experiencing a perfect storm of a rapidly rising prison population with nowhere to put them, and working conditions which are driving staff away in droves.
"Faced with escalating violence, self-harm, appalling living conditions and prisoners left with nothing to do all day – the human cost of this crisis is shameful."