Here are some of the free apps that you can find on google playstore, suitable for android devices

• Offline dictionary - https://play.google.com/store/apps/details?id=com.krishnendu.offlinedictionary

• Math workout (Offline) - Numeracy skills - https://play.google.com/store/apps/details?id=com.akbur.mathsworkout

• Kids place (Offline) - Parental control - https://play.google.com/store/apps/details?id=com.kiddoware.kidsplace

• App usage - tracks how much time spent on each app - https://play.google.com/store/apps/details?id=com.a0soft.gphone.uninstaller

• Word search/Grammar (Offline) - https://play.google.com/store/apps/details?id=com.quelaba.sopaletras

• K9 browser - Safe kids browser - https://play.google.com/store/apps/details?id=com.bluecoat.k9.android

• Wikipedia online - https://play.google.com/store/apps/details?id=org.wikipedia

• African quiz (Offline)- https://play.google.com/store/apps/details?id=com.gmycinstudio.triviaquiz

• Maps - https://play.google.com/store/apps/details?id=com.google.android.apps.maps

• Kiwix, Wikipedia offline - You can download wikipedia for schools(5gb), or wikitionary etc - https://play.google.com/store/apps/details?id=org.kiwix.kiwixmobile

• WPS Office - Reading docs/pdf - https://play.google.com/store/apps/details?id=cn.wps.moffice_eng

• Math tricks - https://play.google.com/store/apps/details?id=example.matharithmetics