Katakana: ガッコ

Roman word: gakkou (Gacowu) is a reference in brackets, hehe.

The first k of the two kks here is to promote the sound, so you have to pause and prepare for the later pronunciation.

Immediately after ga pronounces, press the middle and back of the tongue against the maxillary cavity, pause for about half a second, and then pronounce ko and U in turn.