  We present in this study flux-calibrated integrated spectra in the range
3600-6800A for 18 concentrated SMC clusters. Cluster reddening values were
estimated by interpolation between the extinction maps of Burstein & Heiles
(1982, AJ, 87, 1165) and Schlegel et al. (1998, ApJ, 500, 525). The cluster
parameters were derived from the template matching procedure by comparing the
line strengths and continuum distribution of the cluster spectra with those of
template cluster spectra with known parameters and from the equivalent width
(EW) method. In this case, new calibrations were used together with diagnostic
diagrams involving the sum of EWs of selected spectral lines. A very good
agreement between ages derived from both methods was found. The final cluster
ages obtained from the weighted average of values taken from the literature and
the present measured ones range from 15 Mr (e.g. L51) to 7 Gyr (K3). Metal
abundances have been derived for only 5 clusters from the present sample, while
metallicity values directly averaged from published values for other 4 clusters
have been adopted. Combining the present cluster sample with 19 additional SMC
clusters whose ages and metal abundances were put onto a homogeneous scale, we
analyse the age and metallicity distributions in order to explore the SMC star
formation history and its spatial extent. By considering the distances of the
clusters from the SMC centre instead of their projections onto the right
ascension and declination axes, the present age-position relation suggests that
the SMC inner disk could have been related to a cluster formation episode which
reached the peak ~2.5 Gyr ago. Evidence for an age gradient in the inner SMC
disk is also presented.
