The students from Workington Academy helped to clear the weeds around Mill Field, near Hall Park View in Workington.
Himalayan balsam is the largest annual plant species in Britain and can grow and spread quickly and affects areas including river banks.
The event was organised by Workington Nature Partnership, a joint venture between Workington town council and Allerdale council which aims to improve natural areas in and around the town.
The sixth formers filled 70 bags of Himalayan balsam in just over an hour.
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