This idea is at least a simple concept but, I know from experience, that it is not necessarily simple to implement. Basically I would like to see practice points for spells awarded only when the spell cast is used in the correct context, i.e. a situation in which it has some benefit.
The reason this only really applies to spells, is that any other skill already needs to be used in context to gain practice points (Weapon skills require you to use the type of weapon, mining requires successful mining attempt and so on).
What I dislike seeing is players standing outside the Magic Shop and casting the same spell many times just to get the practice points for the skill level. It's not really in the RP spirit I think.
Obviously the issue is how do you determine context?
For some spells this is easy. Attack and healing spells simply need to affect the target in the way the spell was intended to work, i.e. damage or heal the target. The real problem comes with spells such as buffing spells and other preemptive spells such as Armour (sorry I'm English

) and the like. The only solution I can think of, at present, is to award retrospective practice points for these spells. As an example, casting an Armour spell would only result in practice points being awarded if the target of the spell was in combat (or another situation in which Armour would be useful such as a rock fall) during the spell's duration; in which case the caster gets the practice points as the spell was cast in context. Obviously, if the spell has a really short duration then this makes it harder for the novice spellcatser to gain practice points as it required much more precise timing to be cast at the 'right' time, but is that really a problem or actually a fact of life?
This represents learning about when it is the right spell to cast, which is, I think, one of the biggest deciding factors in what makes a truly great spellcaster, not the amount of spells they know of the amount of Mana they have.
What do you think?