Your penfriends are in the final year of primary school - Next week they have a big exam and if they don't pass they have to stay in the primary school. There are kids aged 17 in the primary school! If they pass, they will move to the secondary school.
If you want to carry on writing to them, please give them your email address or social media details. Ask for their email address too. Do they have Whatsapp? Facebook Messenger?