Bradford City Football Club has cancelled a contract hiring a college pitch to train nine and ten year olds after fireworks were flung towards them as they played.
The players were training on an all-weather pitch at Dixon's City Technology College when they came under a hail of missiles.
Leeds United has also cancelled two training sessions because of concern about what happened about the Bradford players, but is now returning to the ground.
Bricks were hurled at Baildon Trinity Athletic players training on the same pitch last week.
The clubs have reported the incidents to the college which rents them the pitch.
Today the college condemned the incidents - which have not involved pupils - and said the hire charges were a vital income.
Bradford City says it is retaining the contract for two sessions with other young players, but is looking for an alternative for the nine and ten-year-olds.
Trinity Athletic's five teams aged 16 upwards came under fire from bricks on the pitch beside the school in Ripley Street. Officials at one stage considered stopping the sessions for about 40 players because they were in danger.
But the training continued as the attackers ran off.
Team officials say they believe the attackers were children probably living in the area and not connected with the college.
Neil Barlow Trinity's assistant manager, said: "They were large bricks and somebody could have been badly hurt. I think they were just kids but it is so dangerous it has stop."
Bradford City's youth team manager Steve Smith said the club had retained training for other young players on different days at the pitch.
But he said the club was seeking an alternative for the team which had been withdrawn and had ended that part of the contract with the college.
He said: "It was dangerous to the players and we don't feel we should continue."
A college spokesman said security guards monitored the pitch through closed-circuit television and matters had been reported to the police.
He said unexploded fireworks had been thrown at the pitch when the Bradford City youngsters were playing and they had suffered similar problems the previous week.
He said Leeds United had heard about the problems and cancelled sessions for two weeks although they were now returning.
The spokesman added that it was "inappropriate" behaviour losing vital revenue which the college needed.
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