Answer:

PLUS

Answer	Crossword Clue
PLUS	More than
PLUS	And in addition
PLUS	Asset

PLUS	High 80s mark
PLUS	Useful feature
PLUS	In addition
PLUS	Positive
PLUS	Advantage
PLUS	Grade booster
PLUS	"That's not all"
PLUS	Sign in a sum

PLUS	Benefit
PLUS	Good point
PLUS	Grade enhancer
PLUS	Grade modifier
PLUS	Sign in math class
PLUS	Addition word
PLUS	Sign between numbers, maybe
PLUS	And

PLUS	Positive aspect
PLUS	Furthermore
PLUS	Grade elevator
PLUS	Sign that can mean "better than"
PLUS	+
PLUS	"But wait, there's more!"
PLUS	Grade qualifier
PLUS	Bonus

PLUS	Favorable factor
PLUS	Positive sign
PLUS	Cross with addition problems
PLUS	Calculator symbol
PLUS	Valuable quality
PLUS	Good thing
PLUS	In addition to
PLUS	Math sign

PLUS	It makes a B better
PLUS	Favorable thing
PLUS	Positive factor
PLUS	"Not only that ..."
PLUS	Calculator key