Oh did is easy ,
Firstly , we could find some parents volunteers such that there's more Teachers and parents to look after children .
Secondly , pair up the children and before the excursions tell them the rules and Ensure that wherever they go just either tell teacher or parents .
Thirdly and most importantly , there must always minimum one teacher to be at the back and one at the front it is important so that the teacher at the back can Ensure whether everyone is following up and whether anyone go missing .
Lastly , always count the number of students after visiting or exploring one place .