Bob Garton, head teacher at a school in Barking said teachers are "under pressure because of the number of pupils and the mobility in the school".
Speaking to Daybreak's Nick Dixon he said: "We're coping well but it is a difficult situation, we have to stagger our playtimes in the morning, and also at lunch time the children have to come in at different times so they can fit in the hall and the playgrounds."
He said the only way the Government can solve the problem of overcrowding in schools is to give more money to the local authorities to build new school buildings.
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