This is a 2-volume spin-off manga of Girls und Panzer. It is drawn by the same artist who drew the original 4-volume main story. This manga was released in 2015.
In the canon story, Ooarai has only one practice battle against St. Gloriana before facing Saunders in the official tournament. This manga squeezes in another practice battle against Maginot school, which is a French themed school.
Sadly, there isn’t really any real substance in this story. However, it is worthwhile to note that the character design of Maginot school captain is applied in Ribbon warrior series.
Maginot school itself, outside of this manga, barely makes an appearance.
The school has been going through some rough times. They can’t seem to win at all and their moral is all time low. To make the matters worse, there has recently been a revolt within their ranks. Eclair has effectively cast away seniors and have taken over the tankery club.
Now, not everyone is happy with how Eclair handled things with her revolt. Therefore, there are some disgruntled members which further hinders her efforts to apply a new tactic she has been trying.
My verdict on this manga is: Pass it. Not worth it, period.
Not sure of the purpose of this spin-off manga, either. The only good thing that comes out of this short story is that Eclair makes an appearance in Ribbon warrior.