Snape's Worst Memory

[meriaugust]

No: HPFGUIDX 87825

I am just reading the chapter in OotP when Harry looks into Snape's 
pensive, and I have just been wondering why Snape chose the memories 
he did to put into the pensive (mainly the one of his OWL and young 
James Potter tormenting him) and keep the ones (like the one of his 
father and mother yelling) that Harry could see. I would have 
thought that the memories of his parents fighting and the bucking 
broomstick and the lonely room would have been equally as 
embarassing as the OWL day, while the OWL memory has the added bonus 
of showing Harry exactly how stuck up and arrogant his dad and 
godfather really were. Any thoughts? 
Meri