Most linguists believe "<w>, like <y>, is a semivowel (a glide if you will). It functions as consonant but phonetically or articulatory a moving vowel because it moves rapidly from one vowel position to another. Some call it a phonetic vowel, semi-consonant or a vowel in disguise. It is considered as intermediate between a vowel and a consonant in speech sound.
<W> functions as a consonant <w> in ‘wet’, ‘wind’, ’would’ and ‘way’; but as a vowel in graphemes like <aw>, <ew> and <ow>. It forms the second part of a diphthong <u> in ‘raw’, ‘law’, ‘how’, ‘now’ and ‘chow’.
It should be or is being taught as a semivowel.