Children who are learning guitar at school are normally directed to taking a grade 1 Guitar exam with the The Associated Board of the Royal Schools of Music (ABRSM.
Taking an exam like this ensures students get a good methodical education, performing pieces of different styles and periods, learning scales and arpeggios in a structured manner and improving their sight reading and aural skills.
I think children benefit greatly from learning in such a disciplined manner and the increased confidence that comes with passing exams such as these brings benefits across the academic spectrum.
Of course the exams offered by the Trinity Guildhall and the Registry of Guitar Tutors are equally valid and all will gain you a nationally recognised qualification with the National Qualifications Framework (NQF.
From Grade 6 upwards UCAS points are gained which could help in an university application.
If you need any further information about taking an exam please use my contact form.