It's a wise schoolmaster who restrains himself when tempted to write a novel exposing the daily crises from nine to three--unless one keeps it light and simple. The feverish concerns of the faculty room cannot usually be translated into general fare and this novel about the British school system, written by a visiting New Zealander, is so peppered with endemic slang as to be well nigh incomprehensible to Americans. As far as one can make out, our New Zealand teacher, posted in a London public school, is intrigued by a bright but practically illiterate boy embedded in the retarded class. But the enlightened educator suspects he is very intelligent, and strenuously comes to the boy's defense when he is accused of having dropped masonry (with fatal results) on a former headmaster. The novel is shrill with mission and fiddled with breathless ellipses. In all, it's a chore by half and worth scarpering away from.