I read the following in the introduction to the Eizer L'Seifer Movo Likrio, which is the aid to the original book Sefer Movo Likrio, which is used in Lubavitch cheiderim to teach small children the alef-beis.
...The letters themselves have within them holiness (which is why [our Sages] have strongly warned us about the necessity of studying the letters Alef-Beis, etc. and studying the accents, such as Komatz Alef and Patoch Alef etc., for in this study itself lies holiness and a Divine power that arouses the inner powers of the soul, as we see openly that all those who study according to this method have inner Yiras Shomayim [awe of Heaven], and are likely to be aroused towards every Divine concern and subject...Because of the great and tremendous advantage of this - teaching the letters only according to this method [I.e the traditional method of teaching the sound of a letter-vowel combination by first repeating the vowel name, then the letter name, then the sound itself, as in "Komatz Alef - Aw."] - it is a Mitzva and obligation for every Jew to put his soul and heart to this aim, teaching his child and grandchild only according to this method... (Sefer Hamaamarim 5687, p.200)
The above, although a quotation from the introduction to the Eizer L'Seifer Movo Likrio as stated before, is taken from the writings of the Previous Lubavitcher Rebbe, who clearly wanted the alef-beis to be always taught the way you describe, by first saying the vowel, then the letter, and then the sound.
I would have quoted from the actual Sefer Hamaamarim, but I do not own a set myself and I could not find a version online in which to quote from. If anyone could find the actual quote, then please edit it in, by all means!