The claim: Speaking in Swindon, Labour leader Jeremy Corbyn said: "Half a million children are now being taught in super-size classes of over 36."
Reality Check verdict: This is incorrect. Actually about 42,000 pupils are in classes of 36 or more - about 1% of children. Mr Corbyn appears to be confusing statistics. It is right, as the earlier Labour press release said, to say about half a million pupils in state-funded primary schools in England are in classes of between 31 and 35.
Labour claims that pupils in England's primary schools "are packed like sardines" in classrooms.
Jeremy Corbyn said in a speech in Swindon on Friday: "Half a million children are now being taught in super-size classes of over 36."
This is at odds with what his party's press release said, which was that half a million children in state-funded primary schools are in classes between 31 and 35 pupils. That's about 12% of primary school pupils.
That figure is confirmed by government figures from the school census (see tables 6a and 6b), which also says that about 42,000 pupils are in classes of 36 pupils or more, which is about 1% of primary school pupils.
Government rules say no infant school child should be taught in a class size greater than 30 - that's children in Key Stage 1 who are aged five to seven.
That rule can be waived in exceptional circumstances - usually if twins or siblings are admitted to the school, or a child in care has to be given a place.
The official school census for 2016 shows that more than half of Key Stage 1 classes with one teacher have either 29 or 30 pupils in them. Of the infant classes with more than 30 pupils, roughly 95% have 31 or 32 pupils. Classes with more than 32 children in them are uncommon.
Rules on classes sizes do not apply to children in Key Stage 2, which is ages seven to 11.
Between 2006 and 2016, the average Key Stage 1 class grew from 25.6 to 27.4 but at Key Stage 2, where there is no cap on numbers, it has remained stable at around 27 pupils in a class on average.
While numbers of pupils in oversized classes has increased, the number of primary school aged children has increased by about half a million over that period.
Since 2010, the proportion of children in classes of 31 to 35 pupils has risen from 10.6% to 11.9%.