Another word for high-grade

I don't know how you keep such a high grade average.

"According to the son, Josh had high grade samples," Dean answered.

Zinc ores, in the several varieties of carbonates, silicates, oxide, sulphide and sulphate of zinc, have been found in several of the Australian states, but have attracted little attention except in New South Wales, where special efforts are being made successfully to produce a high-grade zinc concentrate from the sulphide ores.

Annaberg has technical schools for lace-making, commerce and agriculture, in addition to high grade public schools for boys and girls.

(High-grade paper.) Summer Yellow.