Well,some people are known to have health related issues.others are known to have unforseen emergencies around such days.. Back then my buddy would bite,chew and swallow his toe nails and within a few hrs he'll be burning with a fever .He'd also initiate gag reflex using his hands shoved at the back of his throat to stimulate throwing up..A combination of fever & throwing up would convince his parents to let him stay at home till he got better.. Another friend would leave home for school then returns back home in a few minutes with stories of how she noticed a van following her and she had to cut through the neighbor's fence to escape back home for fear of being kidnapped..Her parents would be terrified and would let her stay at home ... But you can outright tell your parents you don't wanna attend because of your speech situation and they should be able to cover for you if they really understand your struggle.good luck