Well, the English site of wikipedia is not that informative to this. I only have the German site as quite a good source:
http://de.wikipedia.org/wiki/Schlesische_Aufstände. There it is a link to a Polish site, however I do not know that quality as I do not speak Polish.
Anyway in 1919- 1922 there were three uprisings. The first 1919 one was started by Polish combattants and failed, although they were able to achive an amnesty for the imprisoned people. In 1920 the second uprising took place after pro German demonstrants destroyed some Polish stores and 10 mining workers were shot by ending a strike. It was ended 5 days later when it was granted access also Polish to the security organs.
The third and longest uprising, on which I was aiming, took place in 1921, shortly after the plebiscite. This plebiscite was a great setback for the Polish as the majority of Silesians, even many Polish, voted for Germany and the Italian- British plan for dividing Silesia was refused by the Polish. Although officially the Polish government was against the uprising, they nevertheless helped them as they sent "volunteers" to upper Silesia. At the first time only the Italian troops did try to stop the Polish, but not the French. As the Reichswehr was officially not allowed to fight there, too, the German militias there, of course supported by the Reichswehr, formed the so called Selbstschutz Oberschlesien (SSOS, has nothing to do with the Nazi SS) to prevent the Polish taking over Upper Silesia. The greatest clash was at St. Annaberg, where the Polish forces were beaten and had to retreat. Because of Allied pressure peace again ruled soon after, when the Polish were forced to sign a cease fire, which was critized by the Polish military leaders.
About three thousand died on both sides.
Adler