Here are a few driving schools that English-speaking students have been happy with in Helsinki area:
CAP (12 or so locations in Helsinki and Espoo, at least Kamppi serves in English)
Epic (7 locations in Helsinki, at least Kamppi serves in English)
Street Smarts (Otaniemi, Espoo)
Symppis (Kaisaniemi)
Unreviewed ones offering service in English
A+ Driving School (Sörnäinen)
Autokoulu Pasila (Pasila)
Eco (Kivenlahti, Espoo)
Helsingin Liikennekoulu (Etelä-Haaga)
Kulmis (Viikki, Laajasalo and Myllypuro)