Images of the Chalet School in Tirol are much more common than those of the school in Britain. In fact, I have only one such image in my collection.
This illustration from a hardback version of Three Go to the Chalet School clearly shows a neo-classical bulding, complete with columns. This is quite a fair representation of Plas Howell as described in Gay Lambert at the Chalet School (see below).
"...at last they reached a broad drive with high wooden gates set open and a pretty lodge at one side. Up this they went and [past] wide green spaces with tall copper beeches, clumps of elms and stately lombardy poplars. Here and there, may bushes filled the air with a delicious almond scent, and at one point masses of rhododendrons gleamed with buds as yet unfurled. Then [through] a second gate, and [into] the garden proper. A great stretch of green lawn swept up to the house, and tennis courts were netted off at its foot. Nearer to the house were flower beds filled with standard roses [and] wallflowers, in blood-red, gold, and mahogany gowns, added their sweetness to the air. And above all rose the great house, once white, but now weathered to gracious tones of grey. [It] stood on an embankment, and a broad stone terrace ran round it, fenced off from the grassy banks...by a palisading of low stone pillars. Leading up to the great front door were semi-circular steps, and tall, classical pillars with beautifully carved capitals." - Gay Lambert at the Chalet School
"Along the broad high road they went, turning in at heavy iron gates... A long avenue, with meadows on either side, then another pair of gates, and they were rolling past a great lawn dotted with clumps of trees... At the end stood the great mansion where the school was houses, with a terrace round it and semi-circular steps leading up to the terrace." - Three Go to the Chalet School (page 44)