"The criticisms must be heard," Labour Minister Myriam El Khomri, who drafted the bill, said on Thursday, while Education Minister Najat Vallaud-Belkacem announced that Valls would be meeting youth representatives on Friday.
Wednesday's one-day general strike and demonstrations brought several hundred thousand people onto the streets.
Worryingly for the government, thousands of students and school students joined trade unionists, in scenes that recalled 2006's protests against a right-wing government's proposed young workers' contract and 1995's protests that forced another right-wing government to back down on retirement and other changes to labour law.
The bill has also aroused opposition within the Socialist Party, with party bigwig Martine Aubry angry at a further watering down of the 35-hour working week introduced when she was labour minister in 2000.
Hardline workers' and students' unions want the government to scrap the whole bill and have called another day of protest on 31 March, while Aubry and less militant unions, who have called their own day of protests on 12 March, have called for it to be redrafted.
The Socialist leader in parliament, Bruno le Roux, has promised "significant improvements", especially on the definition of economic layoffs, which until now has been left to labour courts.
Ministers have issued contradictory messages on another possible change, a proposal to raise employers' social security contributions for short-term contracts in an effort to encourage full-time employment.
Jean-Marie Le Guen, who is in charge of the cabinet's relations with parliament, said it was a possibility on Wednesday but retracted on Thursday, while El Khomri said that the question was "on the table".
Two other proposals are opposed by all the unions - a cap on redundancy payments that labour tribunals can order when they judge dismissals unfair and the possibility for multinationals to base their argument that layoffs are necessary on the basis of their performance in France alone.
Other proposals that worry critics include allowing local agreements to undercut industry-wide ones on working hours and overtime payment, an extension of the hours that apprentices under 18 may work and the possibility of referendums of workforces if there is a division in union ranks.