I have DSL service from a local phone company

[madokie]

I'm paying 39.95 a month for 512 kbps. the last 4 or 5 weeks the speed in the evening slows to less than 100 kbps. Its like it is an overcrowded connection because it works fine from midnight or so until the next afternoon about the time school lets out. What I would like to know is what can I do about it, I can get dialup from another company but it is only 56 kbps which is painfully slow. Aren't the service providers required by law to provide a certain level of performance or am I on my own? this company offers dialup and dsl of 384, 512 and 768 kbps. I would appreciate it if someone could shine a little light on this for me.