SRD: Magic: Arcane Spells: Preparing Wizard Spells said:Spell Slots: The various character class tables show how many spells of each level a character can cast per day. These openings for daily spells are called spell slots. A spellcaster always has the option to fill a higher-level spell slot with a lower-level spell. A spellcaster who lacks a high enough ability score to cast spells that would otherwise be his or her due still gets the slots but must fill them with spells of lower level.
Silveras said:Although the text is placed specifically under Wizards and spell preparation, and is repeared almost verbatim under Divine Spells, the wording is "spellcaster" not "Wizard" (or "Cleric" or "Druid").
The same statements should be in the Players Handbook in the Magic chapter.
spunky_mutters said:Heighten actually raises the spell's effective level, enabling it to penetrate a globe of invulnerability (possibly), and affecting the save DC.
Why are bards barred from doing so? I don't remember anything in the bard description that says they cannot. Indeed, I believe the bard description references the sorcerer description...Darklone said:The thingie for spontaneous casters is IIRC in the sorcerers description. At least in 3.0 it was possible for a sorcerer, but not for a bard.
I am not 100% sure (3.0 seems so far away), but the sorcerer spellcasting description mentioned explicitely that he could use a higher level slot on low level spells while the bards didn't say that... If I am right.Lord Pendragon said:Why are bards barred from doing so? I don't remember anything in the bard description that says they cannot. Indeed, I believe the bard description references the sorcerer description...
Spells: A sorcerer casts arcane spells. The number of spells a sorcerer knows is not affected by his Charisma bonus. The spells a sorcerer knows can be common spells chosen from the sorcerer and wizard spell list, or they can be unusual spells that the sorcerer has gained some understanding of by study.
A sorcerer is limited to casting a certain number of spells of each level per day, but he need not prepare his spells in advance. The number of spells he can cast per day is improved by his bonus spells, if any.
A sorcerer may use a higher-level slot to cast a lower-level spell if he so chooses. The spell is still treated as its actual level, not the level of the slot used to cast it.
To learn or cast a spell, a sorcerer must have a Charisma score of at least 10 + the spell's level. The Difficulty Class for saving throws against sorcerer spells is 10 + the spell's level + the sorcerer's Charisma modifier.
Spells: A bard casts arcane spells. The bard casts these spells without needing to memorize them beforehand or keep a spellbook. Bards receive bonus spells for high Charisma, and to cast a spell a bard must have a Charisma score at least equal to 10 + the level of the spell. The Difficulty Class for a saving throw against a bard's spell is 10 + the spell's level + the bard's Charisma modifier.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.