Pete Edwards was among the last pupils at the Ironbridge CofE School in St Luke's Road, the building of which is currently up for sale.
It was dubbed the Blue School because of its distinctive blue bricks.
He says the problem was caused by a porous storm drain culvert and was cured by a new drainage scheme – by which time the school had closed.
Pete, who lived in Ironbridge then but now lives in Stirchley, said: "I was a pupil when it closed. The front yard slipped suddenly around Whitsun 1969. Fears of the then recent Aberfan disaster caused us to be moved into the then empty Coalbrookdale High School.
"This was only to last until the end of summer term when the Blue formally closed. Shortly after this time the Coalbrookdale junior school moved from its building opposite Ed Hiscock's shop into the again-empty High School, where it remains to this day.
"These were times when the area was very much in flux. The Madeleywood Methodist or 'Green' school closed at Easter 1969 mainly because of the opening of nearby Woodside County Primary – this has been since demolished but was near the island on the main road."
Pete continued: "The real problem with the front yard of the Blue was caused by a storm drain culvert that took rainwater from St Luke's Road behind the school, and on down toward the Parish Room. This drain was porous and so fed the slippage.
"In 1968 one of the cottages below the school partially collapsed because of this, leading to the demolition of all between Nick Tart's and the Parish Room. The problems were only really solved when a Telford Development Corporation new drainage scheme bypassed the culvert and took storm water elsewhere, at some time in the late 1970s.
"From that point the yard never slipped further.
"Also in the summer of 1972 a huge drilling programme took place in the Gorge – one of the cores is preserved in the Jackfield Tile Museum. This led to better understanding of the geology and fears of another Aberfan faded.
"Around August 1972 there is a Shropshire Star front page saying 'Gorge Landslip Danger Fades' and it explained much about the drilling programme, done by a firm called Foraky I seem to remember.
"I was quite interested in it as a youngster. The rotary core preserved at Jackfield was sunk by the Lodge Field pond off Woodlands Road and went down 300 feet to below river level.
"All the other bores were shallow 'shell and auger' percussion rig holes done with a machine towed behind a Land Rover, including two bored in and around the grounds of the Blue School.
"These rigs use a winch to drop a hollow stem tool to drill. I well remember the same winch rope being attached to a tree near the school, thus allowing the folded rig to pull itself up the 1 in 2 grassed slope by the Parish Room, all this with a man standing on board the rig to control the winch clutch! It just would not be allowed now on so many safety grounds.
"I was taught when an infant by Mrs Rigby. I got on fine with her but she did suffer poor health at times. She used to bring a small white terrier called Trixie to work with her. He used to sit by her desk.
"The Rigbys had an only child, a son. He was an RAF pilot instructor and was killed while instructing a pupil. The pupil ejected and survived. This took place about 1971-ish. He left behind a widow, she was a Spanish girl.
"I do remember that within the six weeks we were decamped to the old High School both the investiture of Prince Charles and the first manned moon landing took place."
Both these events were in July 1969.
"Also a lovely row of cottages that ran end on to the Golden Ball Inn and which were just below the Green School in Wesley Road were demolished, along with a place called the 'Rock House Chapel' where Methodist meetings were held before the building of the 1837 chapel nearby.
"This was in the same week as the moon landing. Charles Wesley may well have preached there in 1825 because he laid a stone (now eroded) in the boundary wall of the older junior school. It is below the bus stop sign and just above the ornate later 1867 infants school.
"My great uncle Fred was a proud Methodist and very sorry to lose the old Rock Chapel."