In total, 46 pupils and four members of staff from Guiseley School were struck down with the illness as they travelled back from a history trip to France and Belgium on Monday.
Of the 50, 46 had already been released from hospital and the school announced today that the remaining youngsters were now discharged.
Paul Clayton, acting co-headteacher of Guiseley School said: “I am pleased to say that the four students who remained in hospital last night have now been discharged and will now be returning home.
“This has obviously been a worrying time for the families and friends of those who were on the trip and I am extremely grateful for the patience and understanding they have shown as we try to share information with them and keep them updated.
“We will continue to support the students and families as we deal with this incident and I want to reiterate my thanks to the Belgian authorities and others who have been so helpful and caring.”
The school had sent extra staff to Belgium to help those affected.
Belgian news reports said the party became ill with food poisoning as their buses entered the ferry port at Zeebrugge.