[en] Total cross sections, angular, and mass distributions for the reaction π^-p→π⁰π⁰n have been measured for p_π^-(lab)=7--140 MeV/c above threshold. The threshold amplitude was used to determine a value for the chiral-symmetry-breaking parameter, ξ, of -0.98±0.52. The ππ scattering lengths a_I for isospin I=0 and 2 are derived from this result, together with a current-algebra sum rule. The results are a₀=(0.207±0.028)m_π^-1 and a₂=(-0.022±0.011)m_π^-1. These values are consistent with chiral symmetry broken by the Weinberg ππ interaction and the effects of the f₀(975) scalar meson