It was Germany who came up with the name of what was once called Teen Idol pop and is also known as Teeners in Australia.
Its main markets were America and Britain who slavishly copied what America threw our way.
Really the music was just an update of pre rock'n'roll and was not as many believe Tin Pan Alley trying to soften the music-it would have happenned anyway.
Consider that it was Tin Pan Alley who came up with Rock Around The Clock
However high school has many point of recognition-the use of strings,the emphasis on tremolo guitar sounds and the backup vocals is there in abundance
The use of strings especially pizzicato came from Buddy Holly who no doubt recognised that so many Paul Anka singles had used them and wanted to take rock'n'roll music to other untried territories.The year of Holly's untimely death had seen the Drifters at No 1 in the States with a single which was almost classical sounding in its use of strings which included cellos resulting in many black artists dabbling in high school including Sam Cooke who like Chuck Berry liked to pretend to be a teen.Possibly the biggest black star to go the high school route at least for 5 minutes was Jimmy Charles a One Hit Wonder from 1960 with the song A Million To One which would be revived by Brian Hyland in the mid 60s (Charles was no more than a kid who had no connection with the blues)
Many recording sessions would hire the New York Symphony an obvious example being for Brian Hyland.
High School lasted well past the British Invasion-not eveyone was shovelled out as many think and even the Invasion provided its own with Billy J Kramer,Hermans Hermits,Gerry & the Pacemakers.Many newer ones came up through the invasion like Gary Lewis and Ronnie Dove.The music infiltrated Nashville where stacks of it was producedas well as the so called Nashville Sound being based around it
While the bulk of High School was centered around male singers there were nearly as many girls at it many had long lasting careers into the 70s like Leslie Gore,Peggy March and Dodie Stevens.These were usually known as Pixie Girls
Rock critics need to get their facts right before slamming into the music and be aware that High School saw something of a revival during the 70s-the Osmonds/Donny Osmond were digging out songs from the early 60s to say nothing of the number of early 60s high school poppers who had 2nd careers doing the same thing-Tony Orlando,Neil Sedaka and even Carole King