  This paper describes the analysis of UVES and GIRAFFE spectra acquired by the
Gaia-ESO Public Spectroscopic Survey in the fields of young clusters whose
population includes pre-main sequence (PMS) stars. Both methods that have been
extensively used in the past and new ones developed in the contest of the
Gaia-ESO survey enterprise are available and used. The internal precision of
these quantities is estimated by inter-comparing the results obtained by such
different methods, while the accuracy is estimated by comparison with
independent external data, like effective temperature and surface gravity
derived from angular diameter measurements, on a sample of benchmarks stars.
Specific strategies are implemented to deal with fast rotation, accretion
signatures, chromospheric activity, and veiling. The analysis carried out on
spectra acquired in young clusters' fields during the first 18 months of
observations, up to June 2013, is presented in preparation of the first release
of advanced data products. Stellar parameters obtained with the higher
resolution and larger wavelength coverage from UVES are reproduced with
comparable accuracy and precision using the smaller wavelength range and lower
resolution of the GIRAFFE setup adopted for young stars, which allows us to
provide with confidence stellar parameters for the much larger GIRAFFE sample.
Precisions are estimated to be $\approx$ 120 K r.m.s. in Teff, $\approx$0.3 dex
r.m.s. in logg, and $\approx$0.15 dex r.m.s. in [Fe/H], for both the UVES and
GIRAFFE setups.
