I'm looking at that Syllabus that Biggles linked to. If by chance you did mean the PSR-I500 (Indian keyboard), I don't think it's suitable for Grade 6 and up, because Grade 6 and up has certain requirements which the PSR-I500 would not fulfill, such as the following:
- "a minimum of eight registrations" -- The PSR-I500 has only four Registration buttons, not eight.
- "pedal function (with different settings to include sustain, registration change, fill, rhythm start/stop)" -- The PSR-I500 can use a sustain pedal but not a foot controller pedal for doing registration changes and auto accompaniment functions.
- "LFO/modulation function" -- The PSR-I500 doesn't have a modulation wheel.
- "chord settings including fingered chords, fingered on bass and full keyboard chords" -- The PSR-I500 uses a "smart fingering" method that can recognize certain "easy fingering" chords and full-fingered chords, but doesn't have a way to select a specific type of fingering and can't recognize "fingered on bass" chords.
But it looks like the PSR-I500 would be adequate for up through Grade 5.