Answer:

geometry

Answer	Crossword Clue
GEOMETRY	Euclidean topic
GEOMETRY	Euclid's province
GEOMETRY	Euclid's study

GEOMETRY	High school subject
GEOMETRY	Math class
GEOMETRY	Branch of mathematics that sounds like what a grown-up acorn would say
GEOMETRY	Class teaching about planes
GEOMETRY	High school math
GEOMETRY	Euclidean subject.
GEOMETRY	Schoolboy's problem.
GEOMETRY	Euclid's forte

GEOMETRY	"There is no royal road to .....": Euclid
GEOMETRY	Class of planes?
GEOMETRY	Euclid's subject
GEOMETRY	Plane class?
GEOMETRY	Certain math class
GEOMETRY	Course for planes?