Outraged parents were furious after Muslim pupils were given a raspberry mousse containing 'pork' at school.
Bosses at Greet Primary School said they were probing the error after pupils were served up the dish at lunchtime on Wednesday
The school apologised in a letter sent to parents which said 'the error is totally unacceptable'.
Pork is prohibited in Islam leaving Muslim parents furious about the mistake.
One parent told BirminghamLive : "My child was extremely upset and wouldn’t stop crying and refused to go back to school."
A spokesperson for the school said it should never have happened and expressed disappointment at the mistake.
In a letter following the incident, the school said: "The error happened during out first lunch sitting when classes in Year 1, 3 and 5, as well as Reception classes, were having lunch."
An alarmed parent, who asked not to be named, said: "This is totally unacceptable as 90% of the school has a halal diet. This has left many parents extremely angry and are fuming.
"We have tried asking the school questions as to how and why this has happened but we are told by staff we have addressed the matter and if we didn’t notify you then you would have been none the wiser.
She added: "We parents feel the school are not understanding the impact of this on the children and parents it’s having. We send our kids to school thinking they are safe but are now left with a lifetime scar of being fed pork gelatine which is forbidden to Muslims."
In the letter written to parents, it said: "The error happened during out first lunch sitting when classes in Year 1, 3 and 5, as well as Reception classes, were having lunch."
A spokesperson from Greet Primary Schoo said: “Earlier this week, during the first lunch serving, staff became aware that a mousse was being served that contained pork gelatine.
"The dessert was immediately removed from the menu and replaced with a halal alternative.
“While we are fortunate that this issue was picked up very early on during the lunch service, and we currently believe only a handful of children ate the mousse, it clearly should never have happened – particularly given the strength of our Muslim community.
"We immediately wrote to our parents to inform them and offer our apologies.
“We share our community’s frustration and disappointment that such a mistake was made, and have launched an investigation to understand how it occurred.
"As part of this, we are looking at whether this was an ordering, supply or delivery issue, and will seek to understand if there is anything more we can do to stop such an event happening again in the future.”
