[R] specifying an unbalanced mixed-effects model for anova

[Murat Tasan]

hi all - i'm having trouble using lme to specify a mixed effects
model.
i'm pretty sure this is quite easy for the experienced anova-er, which
i unfortunately am not.

i have a data frame with the following columns:
col 1 : "Score1" (this is a continuous numeric measure between 0 and
1)
col 2 : "Score2" (another continuous numeric measure, this time
bounded between 0 and 100)
col 3 : "Class" (a fixed-effects factor with 4 (ordered) levels)

i have ~2000 observations, but unbalanced w.r.t. the "Class" factor.
each observation has a distinct "Score1" and "Score2".

i'd like to try a mixed-effect anova model where "Score1" is the
dependent response, and "Score2" and "Class" are the explanatory
covariates (with an expected interaction between them).

naively, i simply tried:
aov(Score1 ~ Score2 * Class)

but i'm pretty sure this treated "Score2" as a fixed-effects covariate
with a single observation per level.

can anyone help guide me to the correct model specification using
lme(...)?

thanks much for any help!