Encouraging students to revise?!

Students at my school need an awful lot of chivvying along to revise - they will come into school on a Saturday morning for revision sessions, but getting them to revise in their own time and on their own is really very hard.  This is why this year we have decided to try and reach them on their own terms - we have relaunched our department blog (previously only used to send information about our blog from France to the students' parents at home) and fill it with - hopefully helpful - bits of advice for the students.  So far, we've tried sharing a walk-through of the writing CA mark scheme, suggesting apps for their phones and other gadgets; we've just started a hints and tips feature which we intend to run every other day for the next three weeks as the exams get closer.  On our twitter feed (@CHTSMFL), we are trying to offer hints and tips regularly for how to approach certain bits of the exams, and some revision ideas for the students.  I just want to encourage the children to revise for their exams - those with really supportive parents who understand the importance of the exams will revise, and a few of their friends will as well, but I really want to start to tap into the others ...